Post lava Vader had a lot more glaring weaknesses, mobility being the biggest one. He literally walked everywhere because you don't run with heavy metal prosthesis. He had to try and make up his lack of mobility with the force, mostly with choking bitches and throwing shit at people (like with Luke in Empire Strikes Back.)
Luke in episode 6 was very similar in strength to Vader in episode 3 pre-Lava. The main difference was Vader used his hate and anger which made him stronger, though a lot more reckless. It made him stronger but also is why he became lavaman.
His relative strength in the Force was pretty static post Ep 3. Vader in 3 was probably the most powerful individual that has existed and maybe even will exist in Star Wars canon. It served as a reminder that the Dark Side has some pretty glaring weaknesses despite making you a badass child slaying Dark Jedi.
RIP those kids.