A heavier (considerably heavier than the stock engine) engine will affect your sol's hability to do nice cornering (wich is one of the best things in a sol). The extra weight is located beyond the axis, that's why it's non desirable.
On the other hand, heavier (larger) engines usually give you more power.
If you want to do 1/4 mile trials or that kind of things, go for the large engine.
But if you want to make high speed turn, go for the light weight engines, and increase the performace with other mods.