CPSII roms, amazement yet confusion?

I've searched the net trying to find an answer but couldnt find one specifically for this.

So recently I acquired a Wii console with the SD card and all the roms, emulators etc such as Retroarch which included the final burn alpha and had the Capcoms CPS1, 2 & 3 on there.

To my amazement xmen vs streetfighter played flawlessly, and same with the other capcom fighters. I was unsure whether it was my eyes because I can't understand why people are paying a lot of money for games and consoles (yeah I understand the collecting , real feel of the hardware...)

The reason I ask this is because I just forked out over a £100 for a few capcom fighters for the sega saturn (plus an action replay cart).

So do these roms/emulators have any glitches or any considerable amount of difference to warrant me playing the real deal instead of these? I understand these are emulated from Capcoms arcade games but I assumed that they would be of lower quality?

So basically what I'm asking is ; do any of the classic capcom fighters (or any other fighters for that matter) play any lesser quality or speed than they're best console version (ie the saturn/dreamcast) ?

As the titles suggest; amazed but scratching my head somewhat.