With LFS you don'r have the benefit of repositories to find software. Apart from a few sources hosted by LFS, you have to find sources for everything yourself. With Gentoo you have their repositories which helps simplify things.
LFS is great for learning, and a wonderful exercise, though, certainly for me, just keeping the system up to date became a full time job. If you are building a system that you actually want to use, go for Gentoo.
That's not to say LFS can't be used as a day to day system (many people do), but I found it too demanding on my time for that.