Performance-wise, Dogslife & Life are extremely similar & both are using the same codebases. I hear that the voice recognition is more consistent on the Life series, though this is just a rumor & and I can't vouch for it.
As for going around in circles this is always a result of poor lighting and not because of the DogsLife programming. The AIBO I have with me right now does that at times but never has trouble when there is a solid light from above.

(Everyone on AIBO-Life.org would be happy to answer these questions as well- come over and sign up! :-D )