figure out your collection goals and purchase based on that. I personally wanted to have a motherboard dedicated to my MVC2 cart, so that I don't need to unlock the characters every time. Yes you can use that new hacked rom and netboot to get instant unlocks now, but that's not really the same as collecting an original arcade equipment setup. To each their own.
Ultimately I ended up wanting to have a dedicated mobo for my MBAA as well, with a real H BIOS. Sure there's the multi region rom out there now that is based on H, but I again I wanted a completely stock setup for it.
Now I also have a gundam setup with 2 motherboards and 2 carts... need to find some communication pcbs, as I gave mine away previously. So that's a small factor, do you ever see yourself playing a Naomi linked game? Then you need at least 2 motherboards.
I am an originals collector, but I also appreciate the convenience and affordability of doing netboots. It's also a great way to try games out before actually purchasing them. I have a bunch of GD-ROM drives, but never use them anymore. I also have a Naomi 2, because I like collecting the arcade motherboards Sega made.
Depending on the cabinet you are planning to use you may need a Sun PSU. You might need different JVS IOs depending on cabinets so factor that into your budget. Going netboot is cheaper than buying games, but it's still expensive. You may need to shell out for some tiny little harnesses... which hurts, or build your own cables.
tl;dr
- Do you like beach spikers/drivers where the naomi 2 is required
- Do you like original setups or do you want convenience/affordability
- Want to try linking games? You'll need 2 motherboards
- Accessorizing ain't cheap