Well, Paul is favourite beatle in BIG part because he is an ethical vegetarian and an animal rights activist. In fact, I found a magazine in some moment in the nineties of his 1990 or 1993 tour in my house and there was a page about PETA and another of an ecologist group. I mean, I liked him because of that BEFORE I liked The Beatles or any music at all. Before that I had just felt so lonely about that. It was really a big deal. It meant a lot.
Apart from that, many of my favourite beatles songs are his, and not only the most known, but many far less known.
And I like a lot his post - Beatles music. (And John's and George's also).
He is a great bass player.
And his attitude. Nice, unpretentious, positive, thankful of life. Quiet. John was very funny, and witty, and I like him, a lot, but he was just really hurtful sometimes... and agressive. I mean, Paul never (almost, not after 1971 anyway) dissed John, meanwhile John had, even in his 1980 Playboy interview, a certain ambivalence towards him... trying on one hand to diminish his work, and praising it on the other hand. He was evidently insecure and jealous.
Love them all, anyway.
All you need is Love.