Would you say that iComp's 1233 accelerator with a 55 MHz cpu would be not so good of a choice, and finding an 040 is better?
What can I say... my old Apollo 040/33Mhz was MUCH, MUCH faster. Now I have 030/50Mhz and it is like... SLOW (030 is great to WHDLoad and to play a little with Workbench - everything works just slow)
You can look at numbers (MIPS etc.) and compare 030 vs. 040, but there is also one thing I (I know, just me

)noticed the most AGA is speeding up with faster processor which is really nice and you can install various "patches" that makes 040 very nice CPU.
With 040 you can try to emulate Mac and I was running MacOS 8.0 on my O40 with AGA and I was VERY happy (It works better then AmigaOS...).
EDIT: BUT you can get nice ("new"!) 030 from Jens

. They are very nice! It is on my wish list for one of my A1200...