Ilfosol-S and ID-11(=D76) are my favourite developers for emulsions up to EI400. They have a very similar tonality with Ilfosol being maybe a little sharper for the same granularity. Ilfosol-S is a liquid concentrate for one shot use, i.e. you do NOT make a stock solution as you do with powders like D76/ID-11. Thus at the usual 1:9 dilution you will get 8 rolls out of a 250ml bottle with 10ml left over if using Paterson tanks. 3.8L of D76 will give you 25 one shot doses of 150ml each assuming you use it 1:1 and discard after use.
I actually reuse my ID-11, a 1L pack does me for 12 rolls, increasing the development time by 10% after every second roll. Many people will tell you not to do this, but it works for me. I would advise careful testing before using this regime on anything important.
Then there's shelf life. Ilfosol-S is notorious for only lasting a few weeks after you open the bottle, but the small bottles help ameliorate this. ID-11/D76 lasts indefinitely in powder form, the stock solution should last 6 months (often more) if all air is excluded from the bottle.
Finally I've tried Ilfosol on Ilford Delta 400 and couldn't recommend the results. ID-11/D76 was better. Tri-x is one of those films that doesn't seem to mind what you use. I don't use Tmax.
As with all these things, your results may (read:will) vary from mine.
Hope this helps,
Mark