Back when I shot film in high school I recall liking T-Max 100. In my current foray back into film, I have found myself preferring Ilford Delta 100, which is very similar. Part of it is indeed the T-Grain emulsion but it may also be I haven’t really looked much at 100 speed black and white film.
In the 400 speed, I wanted to like Delta but I have to say I am really coming around to HP5+. It’s flexible, punchy, seems fairly forgiving and it’s rather inexpensive. The more I use it the more I like it, in fact. Helps too that it pairs well with Kodak HC-110 development (which is quite inexpensive). I do have more 400 speed films I want to try, such as Pancro 400 and StreetPan 400 (both new films on the market). So far, though, HP5+ is pretty dern hard to beat!