My two picks were Xbox 360 and Nintendo DS, here's why.
To be honest while the PSP is great for custom firmware homebrew, the flash card features for a DS seem to be so much more simpler if using a proper card like DSTWO, overall I find less games appealing on PSP and while DS games are much more simple and there's a lot of trashware games, if you know what you're looking for it's a cheaper option and you will get some decent games.
Xbox 360 is perhaps not the most perfect of game consoles, but it seems all three of the new generation consoles have their fair amount of cons each. I like the great selection of shooters and indie platformers on the Live marketplace, but the increasing costs of the Gold Live Service make me turn away from playing online and sticking with the free services while still reaping the benefits of things to buy on the marketplace like new levels and installed games. While the hard drive options are terrible if you go the official route, you can make your own Xbox 360 Hard Drive if you do some research capping out at 250GB for close to $50 and all you need is some time, know how, and it will perform just the same if not better than a hard drive with a logo on it. Though due to the lack of homebrew, I think my opinion will change in the near future and I will move on towards favoring the Playstation 3 which has recently adopted the homebrew scene. There is one thing that scares me however is that if your PS3 ever experiences the "yellow light of death" aka ylod, Sony will not freely fix it whereas Microsoft will fix the "Red Light of Death" problem that plagues many of the old xbox 360 consoles at no extra cost and get it to you quickly back as soon as possible.