Okay, here's my two cents about what you should consider:
PC-FX:
Not compatible with any other NEC hardware.
Hardware looks cool, IMO.
There are about 100 games for the system, most of which are anime/FMV titles or RPG/strategy games that require knowledge of Japanese.
There is one shooter, "Choushin Heiki Zeroigar", which is pretty good, and also a nice shmup collectible.
There are a handful of other great to decent action games, such as "Chip Chan Kick", "Zenki" (not worth the high pricetag for gameplay alone), "Last Imperial Prince", "Battle Heat", et al
Expect to pay around $150 for boxed hardware and another $150 for a complete Zeroigar.
However, if you don't own any PC-Engine system yet, I would stay away from the PC-FX for now, as it's far less "essential", and especially doesn't offer that much in the shmup department.
SUPER GRAFX:
Hardware will be between $100 and $160 depending on condition, boxed or not, etc.
Hardware looks weird and bad (IMO).
There are 5 Supergrafx games:
- 1941 Counter Attack ($150) shmup, very excellent port!
- Aldynes ($40) shmup, I like this game a lot, but it's a bearer of mixed opinions
- Daimakaimura ($35) platformer, awesome port, better than Genesis version, and more "cult" than the Gapcom Generations
- Granzort ($35) platformer, only played it once, very shortly, seemed okay
- Battleace ($15) 3D shmup, it sucks
There are 2 PC-Engine HuCards which harness the Super Grafx hardware for improved graphics:
- Darius Plus ($25) shmup, good if you like Darius
- Darius Alpha ($1000) shmup, no-resale promo-item, pretty useless boss rush mode of Darius Plus, anyway, this one is only for collectors.
Super Grafx will play all japanese PC-Engine HuCards.
American HuCards (or rather, "Turbo Chips", as they are called) will not run on an unmodified Super Grafx, as the pins on American cards have been rearranged. There are also import adapters to remedy this, but they're somewhat hard to find now.
There are two ways to connect a Super Grafx with a PC-Engine CD-Rom system:
I.
NEC made an adapter called "Rau-30" (not so hard to find, although not sure what it costs on ebay these days) that lets you connect the Super Grafx with the CD-Rom² system ($120) (the original CD-Rom system).
Be warned though, this set up will look REALLY weird in your living room, but it will allow you to play all HuCards and all CD-Rom² games (such as Spriggan).
You can then further upgrade this system by getting either:
- a Super System Card ($15) - which then lets you play all Super CD-Rom² games (such as Gradius II, Akumajo Dracula X)
- or an Arcade Card Pro ($40)- which lets you play all Super CD-Rom² games as well as all Arcade CD-Rom games (such as Sapphire)
II.
Alternatively, the Super Grafx can connect directly to the Super CD-Rom² ($150) system, which still looks kind of weird, but at least the colors/design are matched and it definitely is a very "cult" set up if you know what I mean.
With this set up you can play all HuCards, all CD-Rom² games and all Super CD-Rom² games. You can then upgrade using the:
- Arcade Card Duo ($25) - which lets you then play all Arcade CD-Rom games as well
BTW, all American CD games will work on either of these set ups. Only the HuCards are not compatible.
Keep in mind that upgrading the Super Grafx to full CD capabilty will cost likely as much as just buying a Duo or Duo-R, so there is no real (monetary) advantage to be gained by starting out with a Super Grafx.
Personally, I think you will get a lot more enjoyment and longevity out of a regular PC-Engine system (the Duos are the easiest to use). Also, I generally think the CD shooters have a slight edge over the HuCard shooters. IMO, there are more essential CD-Rom shooters than on HUCard.
Anyway, before you do anything, you should probably just emulate Aldynes, to see what you really think of it.