I have LR, YBCR, and Tweedlewink. I started out with YBCR and finally purchased LR when my son was 2 yr.'s old. By then, he already knew everything in Sem. 1. I regret not buying LR earlier and used it in conjuction with YBCR. He can read over 150 words. We are working on him reading books by himself but he prefers mommy/daddy reading them to him instead.
I also bought Tweedlewink around the age 1 and at first he would watch them and then, he did not want to watch them ever again! At one years old he would say, "no tweedlewink, no!". I am going to start them up again...hopefully his reaction is better.
So to answer your question, get both if you can, or LR if you choose just one.