It doesn't matter which hardware you use. If you design and program based on hardware selection then you're doing it wrong.

Design and write your game to interact with a generic hardware interface class, and create a NullDevice child class uses that interface as its parent and stubs out all necessary functions with debug code. Write your entire game using this on your PC/Mac. Deal with hardware later.

When the time comes to actually build and test with real hardware, simply create a new child class using the interface you previously defined that correctly communicates with the board set you want to use. Replace the NullDevice class' instance you've been passing around with the real hardware class' instance.

Vuala game complete, debugging easy.

A good baseline start is to assume:

32 direct input switches
64 input switches via an 8x8 matrix
at least 8 if not 32 high/mid power outputs
64 lamps via 8x8 lamp matrix controller OR some form of LED driving board
Audio comes from the PC and gets fed into some amp
Screen comes from whatever you want- DMD, VGA, DVI, HDMI... your choice

Design your game on paper first to get an idea of what you need

http://pinballrehab.com/1-articles/solid-state-repair/repair-guides/146-switch-matrix-theory-and-troubleshooting

Understanding switch matrices and lamp matrices are vital in pin design. They can go beyond just switches and lamps to more complex things such as enhanced toy control, dmds, and alpha numeric displays.

Besides- do you really want to piss away money on 64 wires for a switch bus and lamp bus (128 total!) when you only need 16 wires for each (32 total)? I sure don't... I'd much rather buy that extra drop target assembly instead

Actually I tend to do dozens of drawings on paper and some in cad before ever cutting a piece of wood. Pinside and Youtube never sees that part of my design phase. There's a little bit of it on my www.linscustompins.com web page, though it is a bit abridged.

King of the Arcade is different, Mike Testa is spearheading that table's design with me there as suggestion, philosophy, and build support. That game is purely a spit-ball bolt-on-the-table design. I'm in the process of inputing everything into cad now... and it is VERY tedious to measure and rebuild that into a cohesive schematic. I don't think I'll really ever design like this again.

I also never program my games, do a build, test, make changes, do a build, test, etc. I always 100% write game rules, logic, and visuals on my PC in my office. Every once in a while I make a new release build to test on real hardware. For example- Tail of the Dragon was written in 1 weekend while sitting on my couch. it wasn't until like 2 weeks later I tested it on the actual table. I have my custom LinPingine engine built and ready to go, I know what my hardware IDs are and what wire to hook up to what pin so everything works.

I eagerly await this!

Been there, rather buy a product myself
http://www.linscustompins.com/?page_id=239
(also made a lamp matrix and switch matrix back then, though don't have pics of them up)