There are many threads on this topic here on the forum, so you may just want to search for them.

Here's the quick version though.

Neo Geo CD/CDZ - Games are no longer made for this format. Load times are terrible for some games, others aren't that bad. You can find most, not all of the titles for the cart system on cd. There are a few cd-exclusive titles. CD games tend to be the cheapest of your three options, and typically aren't hard to find.

Neo Geo AES - Best possible format for home (unless you have a neo MVS cabinet - that's the arcade version). Games can run between $15 - $10,000, so I don't recommend trying to collect for them. You can put together a very nice library for around $50 per game (average) - despite what anyone says. I know, because I'm doing so. There is basically no load time, the games are arcade perfect. In the higher priced games, beware of fakes - they do exist. If you have a US system, it will play US, Euro and Jap games. If you have a JAP system, it will play the Jap, US and Euro games. Doesn't matter. However, your language is basically inherent to the nationality of the system, unless you have it modded.

My recommendation to you, if your main concern is to get the games to play them - by a home AES system and a Phantom 1 converter. This allows you to play MVS games on your AES system. Typically, an MVS game costs a mere fraction of it's AES counterpart, and they are much easier to find. Example - a Rage of the Dragons AES game will cost you about $300 complete, in mint condition. The MVS kit can be purchased new right now for $59. Big difference. Tehre are some MVS exclusives that aren't available in home cart format. The only drawback for this approach is that there are a LOT of MVS bootlegs out there. They work fine, but they aren't authentic.

Hope this helps some.

Steve