I traded in my PS3 for $150 off my Wii U and I definitely not regretting it especially since they announced a new slim version that will lead to even cheaper prices for the original slims. Since my PS3 was a netflix player instead of the blu-ray player I intended it to be, it was kind of an easy decision to trade it in after seeing that Nintendo TVii and how easy it will be for my family to operate it. I would say sell the Xbox 360 but you will probably get more from the PS3.
That is where I am at, I am not using it, I suppose I could get it again, i'll sell both and get a boat load of games, my primary gaming method is PC, Nintendo, etc. I loved my ps3 for The Show, favorite game over the years, and the rpgs were good, but better to sell it then not, and I don't have a slim, its an 80gb (I regret selling my original 60gb that had full backwards compatibility, but never the less).
I think I will end up selling both, knowing the ps3 only has downwards to go, and I am really excited about Nintendo TVii too.
Thanks to everyone for your input!