I am a big fan of Delta 100. My father (when he was still shooting film; he has since converted to 100% digital work) shot almost exclusively TMX in 120 and developed in HC-110, and he got fantastic results in his prints.
Maybe a decade ago or so, I did a fairly informal side-by-side comparison between the two. I found I preferred Delta 100 ever so slightly to TMX. It had enough resolution and low enough grain to make me happy even in 35mm for demanding subjects that needed high-detail rendering, but seemed to have more "character" than TMX 100, which felt rather sterile by comparison. I realize that descriptors like that are ephemeral and more or less entirely unhelpful. But my experience has mirrored that of others here who find TMX to be slightly less grainy, though Delta is by no means a grainy film.
I have not developed Delta 100 in Pyrocat HD yet. I have developed it in Rodinal (didn't care for it; rather defeated the purpose of using a fine T-grain film IMO), HC-110 (good but not my favorite), and instant Mytol (basically XTOL). Of the three, Mytol has been my favorite. It has extremely high resolution and low grain even in 35mm, and achieves full shadow detail when shot at box speed.
I will probably try it in Pyrocat HD at some point, but it would have to do something pretty special to displace FP4+ as my favorite low-ish speed film in 35mm with Pyrocat. I would expect compared to Mytol that you'd get a bit more grain, a bit more acutance, and slightly better shadow separation. And of course the staining.
A picture is worth a thousand words.
Here's a full uncropped frame of 35mm Delta 100, developed in Mytol, and printed on 8x10 Ilford MG FB at grade 2 and selenium toned. It was shot with a #25 red filter which definitely added some contrast. This print was flattened and then scanned on my Epson flatbed at 600DPI. After scanning I just set black & white points and added a hair of sharpness to overcome the optical weakness in the scanner. The goal when scanning fiber prints for me is always to get the most accurate possible representation of what the print looks like in real life, onto the screen. I bring this up because I want to be transparent, but also clear that what you see is not digitally "upgraded" from what the print actually looks like to my eyes.