I used Lyft and Uber during my stay in SF recently.
I do think it's based on preference...personally I like Lyft in the morning because it's actually a nice way to start you day. Chat with a friendly and learning about them is great. Also, if you've had a few drinks and looking for a night out, the Lyft drivers are the best.
But I can see after a long day, you'd rather just relax, Uber is definitely the way to go.
Overall, I prefer Lyft because I like absorbing their energy. Also, learning first hand how connected the Lyft community is, is simply amazing.