While I generally agree with your preference for GSM devices, there's an advantage in that everyone else does too, so Sprint CDMA phones are available used for much less than comparable GSM phones. Sure, the selection's somewhat more limited but there are a number of high-end, CM-supported Sprint phones available for very little money.
Agreed. I got a slightly-used Samsung Epic 4G from Cowboom for $60 about in January 2012. It had been one of Sprint's two flagship models when it launched, less than a year and a half before. It runs the latest CM10.1 and the WiMax 4G coverage is great in Portland, and upgrading in this way allowed me to avoid a contract change or extension.
Because the market for them is so much bigger, the high-quality GSM and Verizon devices seem to retain their value for much longer... which is good if you're selling, bad if you're buying.