[jbearamus]

in an actual answer to the question, my perspective comes from someone who sells Tmobile, Sprint, and ATT
i haven't really had a chance to play with it in depth but i have tinkered with the HD2 a little and I think I found my store's Tmobile demo card so i'll have more to say tomorrow but on the surface I don't see why anyone would want the HD2 over say the TP2.
SOFTWARE
I checked the build version and the windows mobile software and sense are identical on the HD2 and Sprint's TP2 since the recent TP2 update. so the HD2 doesn't really have an software advantage against the TP2
SCREEN
the screen resolution on both devices is the same, 480x800, but the TP2 has it packed into a smaller screen so in actuality, the TP2 looks better even though the resolution is technically the same
SNAPDRAGON
i wasn't doing anything in depth, yet, so i didn't really see the HD2 run faster than the TP2 I did however see the HD2 trip over the initial month -> day -> month transition whereas my TP2 didn't, and for naysayers, yes i ran the task manager and neither phone was running anything outside of Sense. I'll run a little more tomorrow and try and compare because i'm sure its the deeper multimedia stuff where the snapdragon will shine
KEYBOARD
As my signature will testify, I've had landscape keyboards, portrait keyboards, and virtual keyboards, and I hated the HD2's virtual keyboard, at least at first, I'll see if I can grow to like it at least a little but right now I'd take the Hero's on screen keyboard over the HD2's and I definitely would take the TP2's physical keyboard over anything else, ever
Unfortunately from what i've seen on screen shots of the Evo, it has the same keyboard so hopefully, its tolerable or they do something else about it
EXTRAS
The basic Windows Mobile build is the same on both devices is the same however, Tmobile is throwing in a lot of extras such as the included 16GB memory card (vs. TP2's 1) included transformer movies (tilt screen on TP2 makes it exponentially nicer to watch movies/recorded tv/sprint tv on though), barnes and noble software (this caught my attention as I've waited for an official B&N app for years now, although the version of freewareppc seems to be pretty slick) the blockbuster software seems nice but i can't decide how practical it actually is, mobiTV isn't really that big of deal as most computers will have Windows Vista or 7 by now so I can record tv on my computer and move it to the phone anyway, and inflight internet is nice but is probably available to any device that wants to play with it.
NETWORK
very dirty subject as the network can vary by market but you may want to look into Tmobile's network performance in your area, theres no point in having an amazing phone on a semi-functional network which in my case it is, so it's easy for me to shoot down Tmobile based on network performance alone as in the SLC market Sprint is unmatched but like I said, you'll have to check your area specifially
THE ELEPHANT IN THE CORNER
With exception of the TP2 i'd take an HD2 over anything else currently in Sprint's line up but the problem is, the TP2 costs $100 or in some cases $150 more than the HD2 so Sprintgirl, that's going to be the hard part is selling the benefits of the TP2 as being worth the extra $150, now for me the keyboard is enough reason however, average joe consumer may not see it that way
This is just a quick and dirty review and i'll have more on the snapdragon's capabilities tomorrow (hopefully)