There are differences, it's not necessarily BD145's weight that makes it unstoppable. Both are successful if they prevent Metal on Metal Contact, HOWEVER, there is a huge difference in their Centre of Gravity. 230 beys have a very high centre of gravity, making them easier to nudge out of the stadium. BD145, however, has all it's weight just above the floor, and the MW is also lower. That low centre of gravity combines with teh spoiling effect of plastic in many cases to prevent KO's.
Another point is what part of the opposing bey is hitting the wheel. Some Wheels have excellent smash on their top sides (Upper smash, I guess, I dunno, I need to research that a little), and less at the sides. A good example of this, at least with MY wheels, is lightning L drago. The sides are pretty round, and not much pokes out. However, the top has slopes and gaps, which give the bey some form of upper smash. At least, that's what I can discern. A fairer example may be Hell. The sides of it do have some smash, however, if you own one, if it's used, go look where it's got the most dings in it. More stuff hits the top, which has those slopes and bumps, and that's where it's hitting hardest. It's not Upper attack, but it's smash coming from the top, and hitting under an opponent. 145 heights work against 230 because they get underneath (Basalt on 230, however, is too heavy to really be affected, or, it's wobbling due to it's imbalanced nature smashes back and hits them down, I'd need a really fast camera to see this), and hit upwards. Agaisnt BD145, however, a wheel like lightning, with most of it's attack being on it's top surface, can't get under BasaltBD145, so it's stuck using it's weaker side attack.
What I want to see is if this wheel HAS good smash on it's sides. Basalt BD145 is pretty much the PERFECT bey to test that against. Plus, I'm having trouble finding something that can beat it reliably. I figure if LDD can beat Basalt BD145 reliably, it's top-side smash should let it take care of Basalt on 230.
I hope I've explained that well enough, as I'm eating dinner ATM.
Want an example of a bey that has no attack at the sides? Lightning L Drago. Mine, at least, has very little smash, especially compared to Fang or Vulcan.