I have to admit to being a bit of an HTC fan - for the following reasons...
HTC are more honest about offering upgrades - Samsung have made it clear they don't like upgrading older handsets and were it not for Google pressing them, wouldn't have offered half the upgrades they have
I've had experience of Samsung products in the past and their support is patchy at best - their software apps (for desktop connections etc.) are flaky and annoying to use - and poorly supported in themselves.
For that reason I tend to avoid Samsung hardware - when you're going to own a phone for a long period, and if you're a developer (as I am) it's often worth choosing the better supported handset and that will be the HTC.
p.s. Sense is also rather good but each to their own...