Everything is preference but like crank said in some cases the other weapon can be easier.
I tested around 100 hours with both weapons before i decided to choose the stock.
My experience with the original is more about the movement you have to aim sometimes really far behind you, to make a jump or adjust a lot more while wallpogoing.
A lot easier were jumps where you have to get into something like a hole, just because you dont need to adjust with strafekeys/aim.
left wall jumps are as easy as right walls because you have to turn completly the same amount.
I played quakelive and i really like the original but in tf2 it just doesnt help that much if it is centered while acutally playing tf2.
The stock is more comfortable with the right shoots because you can shoot around edges what can be helpfull.
walljumps and normal jumps seems to be easier because you dont have to turn that much.
wallpogo seems for me way easier with the stock (but thats because i am used to i think).
most important is that you stay with your choice you can learn to jump with both weapons but usually you cant do both perfectly because of the muscle memory that is used for consistency.
stay with your weapon thats all