I think we are going be a little bias here in this forum towards the Photon, but seeing how your asking here I think you might be too. :P
I've owned Xrays(and about every other brand car) before and I really like my Photon. Parts are a lot cheaper and easier to get for me. Amainhobbies.com is great for this and only one days shipping from me. Did I mention I love the color red?
Car runs awesome on asphault and thats what I race on. Yeah, like he said, they've fixed past issues with running changes to there kits. The main price tag is alot cheaper too. $380 vs $490 Plus the added bonus of all the quick help here.