Im not dissing powder game or anything but it is simply a childs toy, it doesnt have COMPLEX electronics and heating does it?
Powder game is the almost direct opposite of powder toy, we focus on having a good cross between realistic and fun they focus on Realism (cept for the electronics)
Personally I think the biggest difference is just in how both were written. They have different elements for different things, written by different people.
...But neither one is written for realism or fun in particular. I'm inclined to think both games operate on Rule of Cool. o_O
Anyway, biggest difference between both games? Air drag. Powder game doesn't make particles drag on the air, so when you spawn them they tend to hang around, and don't form slipstreams immediately.
It's run on java which is famous for its multi-platform support While TPT is casted from C (soon it will be C++, but that's not important) which is known by its native code efficiency