Note: You may find some bias and wrong information, Also I wrote a lot.
God: In this season these two were champions, world-classs, legends the top bladers in the world until episode 49. They were equal from what we saw and have an equal score from what we saw, Lui won one battle against Free and Free won 1 battle against Lui, see, equal legends but with Free barely making the cut of being stronger. Free from the start never lost a single battle, those who battled him got squased and served nothing but amussment and boringness to the blader. He was number 1/the world champion in the world, stood over the Big 5. If I remember correctly Free didn't lose a single battle in the World leuge only losing in the World because of his teamamates not being good enough(looking at you Mr.Burns). As for Lui, he defeated Red eye. We know how strong Red eye with Legend is, one shot big 5 member Xander and we know stronger than Ren wu as Boa clapped him. A world class blader but so is Lui. Lui destroyes Red eye, red eye only getting a point because Lui was toying with him. Then the 2 titans Lui and Free battle ae beast, keep on tieing and tieing with burst. Lui won and was number 1 in the world tough the battle wasn't official I don't think he was officialy named number 1 but he beat Free and that all that matters. Then we get into he International bladers cup with Lui and Free being part the Top 4 in the cup. Lui lost 2 times while Free losing 1 and even then it wasn't really a lost because he had to back down due to inurys, these two weren't stop by anybody, not even the Big 5. The entire big 5 was on block B and Free and Lui defeated them all execpt Lui not being Free their battle . On the battle of Lui and Free, Free won 3-1. They are now equal in a win to loss ratio between each other. But we can say Free is stronger cause he has done more than Lui in terms of feats and wins. Then in the end of God, these two legends were kicked out of the number 1 and 2 spots and were now number 4 and 3(Free in the number #3 spot and Lui in number 4). Free was stronger than Lui in God but only by a little, they were equal but Free barley makes the cut. Just want to metion these two are prime examples of why God was such a great season. I don't think God would have been loved by everyone if it didn't had these 2 amazing, legendary, world-class bladers.
Cho-Z: First Lui, Lui wasn't much this season. In his battle with Valt he tied caused they had the writers couldn't have any of he 2 lose. Then Lui battles Fubuki, Rangrio and AIga. He claps them, with ease. But can we really say this was something big? Rangiro and Fubuki were garbage bladers, and AIga wasn't that strong at the time. I may be underestimated the Cho-Z trio but Fubuki and Rangiro who can't say much about as they were trash cans in Cho-Z. In the luinior cup he lost to Aiga because which doesn't make sense, he should havae won and lost later but it is what it is. AFter the Lui vs Aiga macth Lui was nevered showed again. So with what he did we can say he was a 5.5/10 or 4/10 in terms of how strong he is. Didn't do anything really amazing, I mean he tied with Valt but like a said the writers had to and we know Valt is stronger still. Now on Free, I hate to say it but he was superior to Lui. He destroyed Aiga, in both battle agianst Aiga it was 3-0 and 2-0. He destroyed Kyle 3-0, so so far he has done better than Lui, beating Kyle doesn't really mean anything but beating Aiga definently does. He then lost to Phi but so would have Lui. When Free battled Valt with ho-Z Valkrayie, the only reason Free was winning some cause Valt didn't master Cho-Z yet. in the Final battle Valt beats him but again this doesn't really say much as Valt wasn't in full master/control of Cho-Z even in the fianl battle(We knwo cause in the first 2 battles with Hyde he couldn't activate the Cho-Z blades). So Free did way better, would beat Lui if they battled. Why Cho-Z sucks, plot armour and no clear understanding of anything like power levels.
Sparking: Ah yes, the worst season ever in my opinion. Free came first so lets talk Fafnir(Lame pun by me). Free meets the twins, battles them both in 2v1 and 1v1 battles, claps them kind of easily. NAd then we have episode 11 where the tag battles happens. Free didn't lose to Hikaru, let me make that clear, he lost to Valt, Hikaru only helped with the elimation but didn't alone beta him. So Free loses due to Valt and thats it with Free's arc, now we go to Lui's arc and saem thing happens, 2v1 and 1v1 battles against the twins, Lui claps them, well he didn't beat Hygua cause of Lane but come on, no one thinks Hygua would have won. Right? Now with these two battling Lane, Free battled Uranus while Lui battle Lucifer, Free got clapped while Lui at least gave a fight. So Lui did way way way better than Free in terms of fighting Lane. Now I know Free fought Uranus without a sparking bey and not Variant with a sparking bey. But I can't say anything cause Free fricking never touches Luicfer after episode 17, for the entire season, even in their tag battle Free didn't touch Lucifer once.(Talk about Absurd). I wish Free and Lane battled again then we really could say who gave Lane a better fight and also it would be a cool battle. Right now so far from episode 7-20, I say they are about equal, in the Legend festival. They both lost their battle royals, they both won their first tag battles and thats it cause in their second tag battle they wre partners. On their first tag battles, Lui beat Rantaro and Hikaru while Free beat SIlas and Rantaro, they both fight Rantaro and also didn't took out Rantaro in the battle. Free took down Silas and Lui took down Hikaru, Lui burst Helios while Free barley out spins Satan. Now you could say that Hkaru is weakrer than Silas or stronger but still a burst is a burst and a out spin is a out spin. So Lui did better in the Legend Festival. So after the Festiavl arc Lui is better but not by a lot. In the Tag team tournament I'm going to go battle by battle. First battle: Lui won and Free lost, now Free tied with Aiga and Lui won with help from Drum, but Valt<Aiga so Lui is better. Battle 2: Thye fight with each other, now lets look what they did, for Free he eliminated Drum with help from Silas and fought equally with Lui, for Lui he fought equally with Free and that's it. Silas beat Lui but with help from Free and i say it was a 50/50 for this elimation. Also Free saved Silas I don't know if anyone noticed but Free stop a ragging speedy Longinus from crashing into Satan. Free does better in this battle. Battle 3: They both lose to tag team moves(Free losing to sychnor lighting and Lui loses to Spriggan activating LTE). But we could say Free lost to Valt and Lui lost to Lane, Lane is stronger than Valt, and Free lost to a ring out while Lui lost to a burst, but I have to give it to Free, at specifaclly lost to Valt, Valt landed on Fafnir taken him out, LTE still would have activated even if Spriggan didn't help, even with Drum helping Lui lost to burst so I confess to say Free did way better. Battle 4: Free lost to Shu, Shu is stornger than Free, we all know. Lui lost Hygua and Hikaru even when he used Ragging Upper at full power with help from a full power Drum using Tempest Break. Free lsot to Shu by a indiviual clahs while Lui lost to the twins in a 2v2 clash, I say they are both on same level for this one. Battle 5: Lui did better, I'm tired with writing so much, not going to explain. In the tag team tournament with my pints Lui won battle 1,5 and Free won battle 2 and 3 and they are both equal on battle 4. In the end of the day, my fingers are hurting and Lui did better than Free but only by a little. Free and Lui both sucked in Sparking but still had their ups. Lui was bad but as bad as Free so he bets Free but not in really good way.
Free did better in Cho-Z and God while Lui did better in Sparking. In my opinion Free is stronger than Lui regardless what he does, not way stronger these two legend are abput equal. Free and Lui are my 4th and 5th favorite charecters and Burst wouldn't be the same with out these two legend, titans, world-class champions.