Alot of these aerobatic scale planes start showing bad tendicies when they get overweight no matter what the size. If you think they are having problems with the edge snapping out when overweight just wait till you get a hold of a overweight Cap 232. Talk about snap city. You should shoot for around a 25 to 27 percent wingloading on these planes for good performance. The only gas engines I would recommend for 1/4 scale planes are the RCS 1.40 and the MVVS 1.60 other wise avoid the larger 2.4 size engines they are too heavy. Here is a list of engine and plane combos that I think would work well with gas:

Sig Cap 231 w/RCS 140 (good sport plane)
Sig Cap 231 w/ MVVS 1.60 (should have unlimited vertical)
Funtana with RCS 140 (This combo is rumored to come in around 9.5 pounds with and 80" wingspan with unlimited vertical.)

I have heard of some people using the FPE 2.4 on the H9 Edge 540 but have not heard any comments about the combo so I can not recommend it.

To answer you question I prefer a adaquately powered (still unlimited) light weight plane over a overweight pig with rocket like vertical. In 3D the lightweight plane will be alot more capable than the overweight one.