None of them are bad, although I believe the 15Ls feel less like they lose tension, although I would imagine most all of them lose tension relatively equally.
If you are looking at the Prince Nylon, check out Gosen Pro Form Tuff 15l, very similar (if not the same string), and a pretty good deal! Price is excellent and performance is very satisfactory.
I know a lot of people like the Liberty 16g (and liberty in general), but I can't say i'm a huge fan. It's soft, but it doesn't play resilient enough for me to like it. The Forten is also a big favorite with the cheap players, but I find that the different colors play too differently, and the feel is too "slick."
If you are thinking about getting reels of the Prince Nylon, IMO, there's no reason for you NOT to try the Gosen Micro Generic reels.