Akai Katana is available in US and PAL region formats. DFK was released as Resurrection in Europe. Deathsmiles 2 is available as a digital download in the west. Deathsmiles 1's EU localization was handled by Rising Star Games, so I'd imagine it's potentially more like the JP release.
All 3 releases of Deathsmiles are virtually identical now, and all are comparable to the board.
The only differences you run into are having the option to activate voice-add ons via dlc wth the jp release (and the jp standard release does not include Mega Black Label on disc, but the platinum version does iirc)
Everyone will have their own opinion, but I don't think its really worth getting a Japanese unit. You gain access to:
DDP DOJ BLEX Ketsui Mushihimesama
DDP DOJ and Ketsui work fine in Mame, Ketsui has a region-free ps3 release, and DDP DOJ on the ps2 is a fine port anyways (although it does lack black label, but again, that is on Mame, ad it DOES have Death Label, which is awesome).
You'd basically be importing a $400 console, and then dropping almost $100 on Mushi, just to have access to that one game (which is also available on the ps2, the 360 port is more accurate though). I would say at least test Mushi out on the ps2 or in Mame before dropping big dollars on it. The game may or may not be worth the hassle to you.
Oh, and this one catches people by surprise, and should be mentioned: The LIMITED EDITION release of Espgaluda II is region-locked! The Standard and Platinum releases are region-free. No other Cave game is like this, so if you want the LE Futari or Pork/Sweets, go for it.
