So I thought about getting an original Xbox Debug Kit. I would like some advice on them as I know very little about development hardware. How good are they for games? I would like to use one as my main Xbox instead of my retail one. Do they have compatibility issues with retail games or do they play them like normal? Do they use the standard original Xbox A/V Out? If not, what would I need to use them on my HDTV? What price do they normally go for? Last but not least, what can I do with them? If you have any other advice, please let me know.
Honestly, a modified retail box will work better for most cases. Stock, they don't play retail games. You can use RetailGameLoader, which allows most games to run with some issues, but that must be run every time you boot. Alternatively, you have HackDevKitBios, but that causes all sorts of issues including save game compatibility issues. Standard AV out, yep. Prices start at around 150, and usually top out around 250, assuming no games on it. They are meant for testing unfinished code. That is what they are best at. The upside being that you get 128mb of RAM stock. You can play all three Chihiro games that somewhat work on it, but the same can be done on a retail modified box if you buy one that has the RAM added. The other downside is they come with 8gb HDD stock, and have the 137gb limit in the BIOS, so upgrading the HDD isn't the best on these units.
So would modding my retail Xbox be better? I have no plans of making Original Xbox game atm but I may try it out someday. What are the benefits of the RAM upgrade and does it affect game compatibility?
128mb of RAM ensures that any debug games that took advantage of it will work properly. It helps with some emulators and XBMC, but beyond that, essentially every retail game is limited to 64mb so it doesnt make a difference, even if you patch the XBE. It shouldnt hurt compatibility any though. You can still make games using a modified Xbox if you choose to. Really, it comes down to what you want to do. If you plan on playing prototypes that I and others help put out, a debug kit will do most things. But a retail kit with a large HDD will help you really enjoy the Xbox.
If you want space, don't fuck with a debug kit. They're starting to dry up now, like Borman said - you're best to stick with a retail and modify it.