Well coming from someone who repairs these systems for a living, if you were planning on getting one used, make sure it is from a licensed business. You should also make sure it comes with at least a 6 month(better if its a year) warranty this would ensure that the repairer has reballed the chips on the board. Well when it comes down to choosing one its surprising but i would say get an xbox 360 as long as it comes with said warranty. Why? Well not only will it be cheaper but because alot of repairers do not kno how to correctly reball a ps3. This is because they are too afraid to take off the heat plates or dont really know how to remove them without damaging the chip. To tell you the truth the newer 360s are still having its problems, trust me, i have gotten enough of them to kno. There are not as many red ringed ones but the amount of pixelated and warped screen new version xboxs surprise me. if you have any questions feel free to ask me and i will assist you in any way that i can
I must also advise against getting a broken one and trying to repair it yourself unless you have a rework station. X clamp replacements and towel tricks may work a couple of times but it will be just a matter of time before it fails you indefinately.