[aldevo]

Back in 2004 I did shoot Tri-X and HP5+ head-to-head on a test subject and developed the roll in Ilford DD-X to what I expected was the same CI (the test subject was not a step wedge, though). These were my impressions based on viewing the negs under a good quality 7x loupe:

-HP5+ was sharper
-They were more or less the same as far as graininess, but the character of the grain is different (HP5+'s is of a more regular consistency)
-Speed was about the same

Having shot the stuff in the field, those impressions generally hold up. I do think you'll find that HP5+ is sharper in most developers, though you'd have to enlarge beyond 8x10 for that to become apparent - and the two are curiously equivalent sharpness-wise in Gainer's PC-TEA formula. In a contrasty scene, I might also be inclined to give Tri-X about 1/3 stop more exposure (due to its longer toe) in the interest of greater shadow separation.

Gradation-wise, I have always preferred Tri-X. It's a bit contrastier and, for me, it's always flattered flat-lit scenes, yet is still quite managable in contrasty light. I've also felt that HP5+ showed a tendency to compress its mid-tones excessively in certain accutance developers, such as Pyrocat-MC , though HP5+ redeems itself by exhibiting tremendous sharpness in such developers. And I find that HP5+ does manage to give a marvelous "silvery" look to foliage under certain circumstances that I just can't quite duplicate with Tri-X.

That said, it's generally Tri-X for me. Still, I'll be shooting HP5+ in sheets if I ever get around to using my 4x5 camera regularly since I struggle with TXP.