Well I have both, but had pianoteq well before I got LL. For whatever reason, I stayed with LL, just seemed "better" to me. But R2 is very good, too, and I wouldn't hesitate to use it, either.
I don't remember for sure, but I believe that after upgrading to the Sonar version that had the LL Session version, there was a great deal on upgrading to the full version, and I jumped on it. Not sorry at all....