Larry where are you located? I have heard lots of good things about Sprint and haven't really found anything about the Cingular Mobile Broadband. But in theory it should have less latency and faster connection, however I see nothing about it in my searches which makes me a bit skeptical.
I think it depends on where you are. Some people swear by DSL. As I stated my DSL was horrible. I use Cable, and for $40 a month I get a connection that has been down 10 minutes in the last year, with a 40 ms ping to my broker, with 8 mb down and 2 mb up. That is better than a T1 which goes for $400 a month.
Wife is a ATT veep, but I don't use Cingular. Sprint is flawless in every metro. The reception is unrivaled by any other carrier. Go with the Sierra Wireless card. Installation is a snap as it operates as a LAN card.
If you go to the message boards for broadband wireless, you will find that Sprint rules. They won't cancel subs like Verizon does for excess data use. VZ can be a nightmare when it comes to that. With Sprint and VZ both on EVDO, I'm not sure why you would go with VZ. AFAIK, Rev A is the fastest. Regarding DSL vs Cable, I have both. The DSL is strictly for back up. Cable RULES for ethernet connections. You can't get the bandwidth that cable gives with DSL. My cable virtually never goes down. I was going to swith to FIOS based on the reviews but there's no reason to with the stability of Cablevision internet.