I think the Drake/Meek beef changed my view on battles forever. Going in, as a hip hop fan, I thought it was obvious that Meek was the better rapper. I figured the casual+media wings of music/rap would side with Drake, and the streets/"real rap" fans would side with Meek. IE I didn't think either side would truly win enough for it not to be a stalemate....but personally I figured I would prefer Meek.
What happened instead was that Drake surprised everyone with a perfect diss record. Not saying the song is amazing, but as a diss? That shyt was perfect. Perfect beat. The perfect lines. That's really all you need for the clowning to begin on social media. Meek was embarrassed, no one remembers his diss response, etc.
Lupe is a better "rap lyricist" than Kendrick. They're basically in similar boats as rappers. It would come down to the beat and lines.
Beat: I'm gonna give this to Kendrick since he's the bigger rapper, has a better ear for production, and is more in tune with the sound.
Lines: Toss up. I think Lupe would over think things and end up lost with shyt only his fans appreciate, whereas Kendrick would just hit him with some simple but effective lines. BUT Lupe would no doubt have the ability to do it right if he didn't over think. It's a battle, no rocket science.