Apologies if this has been answered before, I've yet to find anyone say otherwise. 

I recently started making some repros for myself as a a hobby, I have the TL866cs and things are going pretty well so far. I noticed that there is a "W" series of the 27cXXX (W27c512 specifically) chips that are EEPROMS and not UV EPROMS. As of yet, I haven't seen any one using these, is there a particular reason why? They're similarly priced, pin compatible and operate in the same voltage ranges for reading and programming. Thanks in advance for the help!

Also, I made a short run batch of PCBs for a 27c322/160/800/400 adapter for the TL866cs that I'll be building out if anyone is interested. 

if you can get them for a good price go ahead and use them. EPROMs are used because they are generally cheaper to obtain.

Great, Thank you!

I'll try asking here before making a new thread. I have a 720 cart that was destroyed and I want to turn it into a Mega Man 2 cart. Both use an SG-ROM board with Mega Man 2 being 256kb and and 720 being 128kb. Does this require rewiring? I'm using a 27c512, ran it through readness and padded the rom but no luck so far. 

mega man 2 is 256 Kilobytes, not kilobits (kb). a 27c512 is 512 kilobits, or 64 Kilobytes. That chip is too small for that game. You need 27c020 or equivalent for 256K capacity. 512's are only going to be good for mostly NROM or CNROM games.
and just a heads up, it's pretty obvious you're learning but in general you're not going to get much help asking how to repro retail games.

Gah, you're right. Not sure how I missed that. I assume it would be similar to an SNROM rewiring then. Thanks for the heads up and patience, I'll stray away from retail game discussion. If it's any consolation, I am mainly in it for hacks and prototypes but I figured it was best to start with some simple projects first.