Details of both can be found here
http://www.lfest.co.uk/
Lfest this year moves to a spot not far from the sea in LLandudno, North Wales! Due to the new site (which has proper toilet blocks, so no portaloos this time!) , numbers are being restricted to 650 this year, I believe to see how well the facilities cope with that number of prople,and I believe the hope is to expand the number of tickets available over teh next few years if this years' event is a success.
Definitely one to go to if you can, and excellent value for money! Solos are well catered for
I can't speak from experience of LFest del Mar (I can't cope with hot climates), but reports I've heard from those who have attended were universally good.