<<<What is seducing in tri-X of course is its tonal range, and I
wondered if it would better suit to platinotypy, just for that reason.
I noticed that one may have huge grain differences when processing tri-X
with different developpers.>>>
Bear in mind, the main wonder of Tri-X (roll film: the sheet film is a
completely different emulsion) is the generous shoulder that lets
highlights record in a way that can be printed in normal gelatine-silver
enlargement. This isn't especially important when you will be enlarging
(either digitally or traditionally) to a negative for the final contact
printing.
Tri-X has also changed dramatically over the thirty years I've been
using it, though with a certain family resemblance. I don't believe the
current incarnation is as changeable in grain structure with developer
choice as the ones I grew up with.
Bottom line: to shoot 35mm for silver enlargement, I still wouldn't use
anything but Tri-X. For negatives to be enlarged for Pt/Pd, I'd go
immediately to TMY.---Carl