They're almost polar opposites. The only thing I can think of is devotion to their cause. Darth Vader fought valliently for the Empire and the Sith, Obi-Wan Kenobi for the Republic (later the Rebellion) and the Jedi.
darth vader
yes
Darth Vader's Master is technically the Emperor when he was a Sith, but when he was training as a Jedi his master was Obi-Wan Kenobi
Weird as it may seem, Obi-Wan Kenobi was 57 years old when he was killed by Darth Vader.
Obi-Wan states to Darth Vader, "If you strike me down, I shall become more powerful than you can possibly imagine."
Anakin Skywalker(Darth Vader), Count Dooku, Obi Wan Kenobi, Chancellor Palpatine(Darth Sidious)
Obi-Wan's body literally became one with the Force.
Darth Vader's old master was Obi Wan.
Obi-Wan Kenobi (Ben Kenobi) dies in Star Wars Episode 4 (IV): A New Hope By Darth Vader (Anakin Skywalker)
Yes, Obi-wan and Darth Vader fight twice. Once on Mustafar, where Obi-wan was the victor, and once on the Death Star where Darth Vader killed Obi-wan.
Darth Maul was killed on Naboo by Obi-wan Kenobi.
All the main chars are Yoda, Obi-Wan Kenobi, Anakin Skywalker, Ahsoka, luke skywalker, Darth Vader,the emperor,boba fett,jango fett,mace windu. All the main chars are Yoda, Obi-Wan Kenobi, Anakin Skywalker, Ahsoka, luke skywalker, Darth Vader,the emperor,boba fett,jango fett,mace windu.