The CPS2 ones are also produced from the Phoenix verisons of the roms which your milage may vary with anyway (those things had to be hacked up quite a lot to run unencrypted and people have reported glitches caused by that in some of them, certain special moves crashing the games etc. )
Really? I thought the Phoenix modification was a "cure" to the dead battery problem and the only solution to fix a dead CPS2 board. So you're saying that it's actually better to have a non-Phoenixed board and to replace the battery every so often?
absolutely, one it's phoenixed it's running heavily hacked code.
The entire process of phoenixing the games involves taking an decrypted code block, and decrypted data block, then (with a few pointers taken from comparing alt region sets of the same revision) merging the areas of decrypted code and data, first automatically then manually by going over a multitude of cases where the sets don't quite match up, or the encrypted bytes happened to match so looked like data etc. Get one wrong, and the game is liable to screw up at some random point. In addition the video registers end up overlaying an area of RAM, so if the game uses that area of RAM the code that accesses it also has to be hacked. Again you have to hack the video register accesses, and any ram accesses that end up accessing the area of ram where the video registers now live. Mess one thing up and you'll introduce subtle bugs that the originals don't have.
Certainly clever, and a non-trivial amount of work to create in the first place, and without doubt useful if a board is well and truly dead, but, keeping your old board alive is the only way to ensure that you're running original code, as the code was meant to run and being able to know that any glitches you see are due to bugs in the original program and not subtle new ones created by the extensive hacking.
On legal ground the phoenix sets could easily be considered bootlegs, operating them in a commercial environment may not actually be legal (Capcom offer their own repair service at cost, and running Phoenix versions on location is akin to running cracked software in the office) Also features of the phoenix sets like bypassing the game region likewise make them even more legally questionable (the games are sold and licensed for use in specific regions)
It's rather sad to see people killing otherwise working boards to phoenix them, because it makes finding truly original Capcom sets harder (and bootleggers in china / hk have been buying up less popular boards, killing them and converting them to more popular titles and now these multi-game boards, so who knows which sets have been lost in that process)
There are still cases where original boards are probably needed to decrypt the games, IIRC the program data is so short on Puzzle Fighter that the only way to decrypt any alt regions that may show up is with a working board, so if somebody was to kill and phoenix a Brazil Puzzle Fighter board just so they didn't have to worry about the battery anymore that would be doubly horrific.
So yes, they're good if your board is already dead, and have saved many boards from being trash (Capcom won't repair boards sold out of their intended region), however, killing boards specifically to use the phoenix sets isn't such a good idea.