Actually, IMO attackers are either equally or more dominant in plastics than MFB, especially with uriel 2 tipped combo's.
The difference is in plastics they can afford to trade weight for speed to gain momentum, and it works very well. Plus, instead of blunt smash they are able to concentrate smash into points due to the sharper, pointier designs, and also execute true upper attack, which is somewhat more effective than plain upward smash (though, Upper Attack requires some smash to function properly, lifting a bey into the air does little unless you also push it outwards).
As for slow moving bottoms, there aren't really any good ones for attack in MFB either tbh.
You must remember that while MFB attack is powerful, MFB defense is also extremely powerful. They are heavier, have better stamina (and thus can expend more of that on grip tips, I mean, RS is basically seaborg 1's tip, but no one would call the latter top-tier), and are generally rounder/lower recoil (even covering a WD with plastic leaves notches and indentations ripe for a smash attacker to hook into, whereas MFB has Basalt, which is basically the concept of compacts taken to a ridiculous extreme.
Actually, that basically sums up MFB’s comparison to plastics. MFB (especially more recent releases, Hell kerbecs onwards) takes everything to wild extremes, and thus equally/more extreme parts must be produced to stay competitive. Honestly, to me it doesn’t seem like a really healthy metagame…
Benjohadi: Actually, upper attack in MFB is near impossible. they rotate far too quickly for anything to properly be made to run up a slope, all you would get is upward smash, and we already had a great wheel for that (lightning). It's not only the lack of plastic-on-plastic collisions that cause this, I've realised of late, but the power with which MFB make contact, everything flies off before it would have the chance to ride any slope. Upward smash is still very good, of course: Lightning dominated for ages and has always been at its best working an opponent from below (though it does have some horizontal smash, enough to get by, it has always been best on lower heights than it's opponents). Basically, you will always get smash before you get upper attack.
I really must update my guide post with this, because after having used plastics for so long, the idea and required conditions are much clearer now than they were then.