In short, look for CDMA ("MarvelC") if you have Virgin, Metro, or USCell, or basically services without SIM cards and have MEID Hex/Dec numbers.
GSM (just "Marvel") for T-Mobile, or basically phones that uses SIM cards.
Here's a post I made regarding the different models according to HTC's site.
http://androidforums.com/htc-wildfire-s/540126-wildfire-s-random-touch-glitches.html#post4682747
You can also check places like Phonearena and Phonescoop for details that HTC's site doesn't show.
HTC Wildfire S CDMA full specs
HTC Wildfire S full specs
HTC Wildfire S T-Mobile full specs
HTC Wildfire (CDMA) Specs, Features (Phone Scoop)
HTC Wildfire S (GSM) Specs, Features (Phone Scoop)
HTC Wildfire S (CDMA) Specs, Features (Phone Scoop)
Update:
This should be interesting.
[INDEX] roms/recovery/guides/kernel/root/... - xda-developers
Update 2:
http://www.snakebytez.com/howto/how-to-root-htc-wildfire said:
Rooting is the process by which you gain better access in your HTC Wildfire operating system. HTC Wildfire has two major rooting procedures depending on your Wildfire S phone. Wildfire S phones can be CDMA or GSM types. CDMA phones do not use sim cards while GSM requires sim card in order for the phone to function.
HTC GSM phones have A510a, A510e and A510b part numbers and CDMA phones only have part number A510c. GSM phones are called marvel while the Wildfire CDMA is called Marvelct or Marvelc. If you aren