Even for people who become deaf post-lingually, and for hearing people, lipreading is difficult at best. So many words look exactly the same on the lips, they ARE exactly the same. Lipreading is never something that can be fully mastered because it can't be perfected, no one can ever lipread with 100% accuracy all the time.
That said, ASL is an entire language. Although people can learn basic signs, to really communicate you need to be willing to learn the other language; no matter what, it will take time. However, especially if taught to young children by fluent speakers, it can be mastered. I'm learning ASL at high school age, from a community college, and I will probably never sign just like a native speaker. This doesn't mean that I won't be able to communicate clearly, or that I won't get to the point where I can fully understand ASL spoken to me; I will.
Neither lipreading nor sign language is something easy to learn when you are an adult. However, it seems to me, with lipreading you enter a world constantly trying to catch up, make sure the ignorant hearing person is looking at you, and hoping no one changes the topic or uses vocabulary you've never heard of that can't be explained. When learning ASL, you can, if respectful, learn about and possibly enter a wonderful community of people. You can speak a second language, and, with time, learn to communicate beautifully. I don't think there is much of a comparison.