They've met and had dinner with each other and are said to 'respect' one another. Vince even says he sees a bit of himself as a promoter in Dana White.
I would agree that Pro Wrestling and MMA/UFC are different animals, but they do still 'compete' for dominance in terms of PPV dollars, in which case UFC is owning WWE much of the time except for Wrestlemania every year. [size=x-large]Supposedly, there was even a handshake agreement between Dana and Vince to never air a UFC and WWE PPV on the same nigh[/size]t. If Vince thought they were absolutely not competition in any way, then why do WWE contracts now state they a person cannot ever leave to go work for a mixed martial arts company? Even The Rock said not long before (or after) coming back to WWE in 2011 that if MMA/UFC was as big when he first broke into wrestling as it is now, he probably would have gone to UFC.