Vader was the opposite of Anakin. Darth Vader knew his strengths to a precise degree. He knew his weaknesses and how to safeguard them. This means that while he had far less power to burn than he did as Anakin, he could leverage that power to devastating effect. read more
At the age of 23, (when he was immolated) as Darth Vader, he was the same strength both in, and out of, the suit. It's arguable Vader was even more powerful than Anakin at this point. At the age of 46 (his death) he was stronger in the suit, than he was at 23, out of it. read more
But since he got put into the suit Darth Sidious remained more powerful than Darth Vader if thats the case then Anakin would be alot stronger than Obi Wan too as Yoda said Obi Wan was no match for Darth Sidious. read more