1. My heart wants me to go for a classic refurbed dedicated cabinet from someone like tntamusements. (£1500 delivered to UK for an Asteroids Deluxe for example, though I have still to suss out import tax. Maybe there's a UK company that does similar? Haven't found one).
2. My head tells me a nice JAMMA cab will give me the flexibility.
The 3rd way is a Sega cabinet. What are my options? Can I swap out different types of board such as model 2 or model 3 on the same cab? Tempted to go this way so I can have games like Virtua Tennis and Sports Jam on a nice candy cab or similar. Are there cabs that have a CD/DVD/GD disc drive in them that load games into RAM?
How easy is it to swap control panels so I could consider getting a Daytona or Sega Rally set up? Is that possible at all? Can Sega boards work with JAMMA?
JAMMA will give you flexibility. I don't own a cab myself so I'm not sure how hard it is to swap out different control panels, but board switching is a matter of taking one plug and plugging it into another board (super easy, hence why JAMMA was invented).
Of course you'll run into trouble with JAMMA+ games, games that go beyond 4 direction joystick + 3 buttons + start & coin for each player.
One thing that's VERY IMPORTANT with Sega boards is that they tend to use a different frequency monitor for higher resolutions on the later games, including the stuff ported to the Saturn. You'll want a dual-sync/multi-sync or tri-sync monitor if you want complete compatibility with most arcade games. If you go the JAMMA route, be sure your monitor will do at least 15 and 24hz for the earlier Sega stuff. 15hz and 31hz if you wanna run Naomi/Naomi 2. (Or all three if you want the best)
As Syntesis has mentioned, having a tri-sync monitor is really important. I've got a naomi cabinet and it's screen is only 31hz so I can't run anything on it which is lower. A model 3 is largish and if you want to run it on an lcd you need a special harness on it to make it compatible with a jamma supergun and an a video scaler because it outputs a cga video signal. A naomi 2 system is good because it's backward compatible with naomi games. You could get a gd rom drive for it as the majority of disc based games are cheaper than the cartdrige versions. The only downside is that the disc based game has to be reloaded every time you fire the system up. All depends on how much you want to spend and how much convenience you want from the set up