It's a great film, indeed!
But even Tri-X 400 is amazingly low in grain now. I don't see grain in anything less than 8x enlargements, unless I stick my nose in the prints. I think Efke 100 tends to look much more like the classic "Tri-X look" than Tri-X does!
I tend to use Tri-X, as it is cheap right now as Arista Premiun 400. It is good enough, and I generally prefer the look of traditionally-grained products. However, I use T-Max 400 for pushing in very flat and low light, and when I need to minimize grain when shooting a 400 film.