In my opinion the 637/42 are far more comfortable to shoot than the 342. It's not so much the control ability but rather the comfort factor. The 342 (IMO) has a real violent slap to it. The 642/37 on the other hand, stings a bit but that's mainly due to the exposed back strap. I can shoot my 637 with standard pressure rounds all day with no problems at all.
There was also something bantam grips on the 342 I did not like. They would really tear up my palm, right below my thumb. I prefer the grips on the 637/42 much more than the bantams. You could try a larger set of grips with a covered back strap but then your defeating the purpose of the gun.