they are different in every aspect, h.smoke has:
-fastest walk speed
-ability to relaunch
-pop-up combo with ability to continue into the juggle (damage >50% of lifebar)
-h.smoke is easier to get juggled
-harder to get relaunched
-worse air throw priority (hitbox),than robo has
-more useable roundhouse, can be used as Anti air (into TP-Spear-pop-up juggle)
-more useable teleport (for getaway)
-h.s. is overall more dangerious, rushdown runjabs can be altered into pop-up, so opponents mostly have to sit and block and get the cheap damage,waiting for your run meter to expire
Robo smoke takes 100 times more skill to master. Imo a high level Robo can go toe to toe with a high level H.S. Depends on the skill. In an average situation with two good players, H.S. beats robot Smoke badly.
Well, they are played quite differently as they have completely different combos and a completely different moveset (only move they really share is the harpoon, but i'm pretty sure robo smokes comes out faster for some reason)
What makes human smoke better is that he can lay down high damage combos easier.
For example, off a simple spear, from robo smoke you can get like 30% damage with his 5 hit combo. With human smoke you can get over 40% off of a spear.
Human smokes pop up combo makes him much more dangerous. His comboing ability is better than robo smokes, meaning it will take less mistakes from your opponent for you to win. I'd suggest just reading the character guides for them both on this site, because I'm too lazy to go too in depth.
Human smoke is definitely better, but that doesn't mean robo smoke is bad. He is actually very good. I actually find I'm a little better with robo than i am with human smoke for some reason. I just like abusing robo smokes air throw, it is easier to catch people with because you can be pretty far from them in the air and it will still connect.