I have been reading the threads on these lenses both here and on FM and there is a ton to read through. I compared shots on flickr for both (50L wins, hands down). I have come to the conclusion that there is a lot of disinformation (opinion, really, but not much useful information) and very little substantive information in most of these postings. I also came to the conclusion that either choice is a toss-up as to making the correct decision. It seems like there are two correct decisions with one being slightly less sub-optimal. In other words, there is no incorrect decision.
That said, I will buy one of these on Friday. I was thinking of getting both but I also wanted to get a 70-200f/2.8IS and I don't have the budget for all three.
So, I have devised a tie-breaker, since this is going to be the first significant use for my new 35L/50L, think of Pirates of the Caribbean at Disneyland/world. Do a flickr search like this: http://www.flickr.com …and+pirates+eos+5d&m=text
to get an idea of the scenery. Needless to say, it is extremely dark in there. (no flash allowed)
Using a 5DMkII (full frame) body, which lens (35L/50L) would you take with you through this ride? Is the 35L fast enough? Is the 50L wide enough?
Also, I will probably play around with video while in there (last time we, as a family went through at least 12 times). f/1.2 seems like it would be far superior to f/1.4 in that regard. But, I've never even operated the video after owning the body for almost a year. Never thought to use it...
16-35II
{Panasonic GF1 + 20 1.7 + 14-45]} 
