I use Tmax100 @ 50 ISO and APX100 @ 100 as it's a true speed and they behave in a very similar manner, except for Agfa's stop higher speed. I used AP100 prior to that.

APX100 is the Agfa equivalent of Tgrain the differance is the ISO testing is more realistic as it's based on the Din method of testing film speed, which gives a true speed unlike the ASA method which tends to overstate the true speed.

APX25 (discontinued) and APX100 are T-grain equivalents however APX400 is not.