I knowI can multiple FE's but it's nice to have just one running without going to Windows, etc.
I was talking about one
non-mame32 FE, using different versions of mame for different games as you want. No exiting into windows. Heck, once set up, you don't have to remember which version of mame is needed/best for each game: the FE remembers for you. And if you want to slowly migrate, you can have the FE call "mame32 gamename" to directly start the game, while leaving you mame32 there to use when ever you want.
Not that I'm saying you have to use a different FE than mame32, just they can do a lot of things that mame32 by itself can't because they're separate programs from mame.
Also, "newer mame = slower mame" is a
general rule, and is not true all the time. Different games, PC hardware, and settings matter, too. For example, Rastan runs about 10% faster on my laptop and work p4 computer in 0.106-0.114 than 0.36b15-0.105 (when run at desktop resolution and directDraw), and from 0.36b15 to 0.105 varied only about 3%. Yes, newer = faster. Of course, with different settings, or different games, or my athlon desktop, the test results were different (but not necessarily opposite). What these differences mean are that you should test your hardware and settings and games you play, and see how much a difference different versions of mame makes to you.
Attached are graphs of rastan, mslugX and a few vector games on my laptop, and average FPS after 7200 frames, each version of mame run at least 3 times. "Default" means only FTR/STR, throttle, autoframeskip, and rompath were changed from whatever that version's default setting are. "Auto res" forced directDraw and related setting plus above. The non-labeled forced to use the desktop res plus above.