As nice as the ESB Luke looks, the sculpt just utterly captures Mark Hammil on the ROTJ figured, if you're forced to pick one or the other, I'd go for ROTJ.
Depends on what you are interested in as far as the figures. The ESB Luke has a more elaborate costume and more accessories. I, myself like that incarnation of Luke best. I say...ESB Luke.
The sculpt on Jedi Luke is one of best in the entire line (even with the open mouth). It's definitely worth having in your collection. Especially if you're more of a ROTJ fan.
That being said...I can't wait to get Bespin Luke. :chew
If Bespin Luke turns out as good as the proto I'll put it on the same level as Jedi Luke. But since ROTJ is your favorite movie, that's a good deciding factor.
Also, Jedi Luke has the distinction of being the first (and rarest?) SS SW figure.
If Jedi is your favorite film, then yeah, go with Jedi Luke. Don't let the euphoria of Bespin Luke being a new figure sway your opinion.
Both figures look great and I consider both to pretty pretty iconic images of Luke, which is why I (will) have both. So you can't go wrong with either. But then again, I'll also be getting farmboy Luke when he's released too.
I personally like both, but since Jedi is your favorite film I would go with that one. Another consideration is $$$$. The ROTJ Luke having been sold out a few hours and days after he became available puts a higher price tag on him in the secondary market. The exclusive blaster is a nice piece but not a deal breaker for the figure. I'd say go for the regular Jedi Luke to save some money and order Bespin Luke too! You won't regret either of them.
I pity those collectors who are only limiting themselves to ONE of each character. Jedi ROTJ Luke stands comfortably with Yavin Ceremony Luke and when Bespin Luke arrives there'll be four of them (counting the Hurricane ESB Luke that I've got with light-up lightsaber).
Personally I don't get the whole only get one of each character. Boushh is a tremendous figure and I wouldn't want to have to choose between her and the more iconic ANH Leia that'll be out shortly.