Since you read all of it what was the outcome?
From what I understood the 3L sacrifices a little breathability for a little better waterproofing. Honestly I don't think I'll feel that much of a difference in east coast and Colorado conditions. 3L seems to be the way to go if I were to be doing any serious backcountry or in really wet conditions like Pacific Northwest. Might just go for the cheaper 2L and put the extra $ towards goretex pants and a high quality midlayer.