Yoda was reluctant to train Anakin in Episode II because he said Anakin was too old to start training (even though Anakin was still a boy). However, in Episode V, Yoda didn't seem very reluctant to train Luke despite the fact that Luke was a full grown man by that time. Why did Yoda put up resistance to training Anakin yet he was willing to train Luke?
Note: the idea for this question came from http://www.moviemistakes.com/film409/questions/page2
Luke is their last hope (I know there is another) objections about his age would have to take a back seat to the more pressing threat that by the time Luke turns up on Dagobah there are only 2 Jedi left Yoda and Luke (with luke being a very tenuous Jedi at that).
As Obi-Wan was on Tatooine watching Luke we can assume that part of the plan formulated by Yoda and Obi-Wan when Luke and Leia were split up would involve Obi-Wan monitoring Luke and sending him to Yoda when he was ready. Which Obi-Wan does on Hoth.
I think that yes, Yoda felt that Anakin was too old. Not only that, but also, he felt that Anakin might not be fully suited for the life of a Jedi, partly because of his emotional connection to his mother. I seem to remember that Yoda and Master Windu had some misgivings, which was partly why they were reluctant to allow Qui-Gon to take him as an apprentice. Yes, the reason they gave was that he already had Obi-Wan as an apprentice, and taking on Anakin as well would have broken the rule of two. But even when Qui-Gon said Obi-Wan was ready, they were still reluctant.
The reason Yoda especially was against Anakin being trained was, yes because of his age, but it goes deeper than that. Anakin was too old. Jedi younglings start training very early to be learn to control their emotions and power. However, Anakin had too many emotions and had never really learnt to control them. Plus, he had his mother, who was a point of contention, because as shown in the second movie, she was the reason he disobeyed his mandate to protect Padme and went haring off to Tatooine.
However, Luke was a slightly different case. Not only was he the last hope (whether or not they count Leia is another matter), but he was more level-headed. Yes, he had rough patches where he raced off to find his friends on Bespin a-la Anakin going to Tatooine. But in the end, he is proven to be the better of the two when he triumphs over the dark side and rejects Darth Sidious. Yes, he was a lot older, but he was probably the only one strong enough at that time (physically and psychologically) to beat Darth Vader.
Also, errr, in the movie, Yoda actually was very reluctant to start training Luke. He first tries to test Luke by acting like a kid and then sighs and says, apparently to himself, that he can't teach Luke because he has no patience. Then Luke realised that the irritating little green alien was actually the Jedi master he had been searching for. And he tries to convince Yoda into agreeing to teach him, but is losing the argument until the voice of Obi-Wan joins in and convinces Yoda to teach him. But main point: Yoda was reluctant to teach Luke. Very reluctant.
