I use both HP5+ and Delta 400 for the zone system, well, my own variation of it. I develop films to a CI (contrast index) of about 0.5 to 0.8, which roughly corresponds to N to N+3. For the work I do, I don't need N-. (Quite possibly, a really precise test would show that I get N-1 to N+2, but I don't really care.)(posted 9549 days ago)They both respond well to variations in processing time, which is what you need for the zone system. The Kodak T-Max films are more sensitive to variations, which is bad because it means you have to be more consistent in your processing, but is good because you don't have to extend your processing so much to get increased contrast.
I develop HP5+ in Paterson Aculux, because I always have, and don't see any reason to change. Delta 400 goes in Paterson FX39.
The main difference between these films, as far as the zone system is concerned, is that HP5+ has a gentler slope on the toe. It is said that HP5+ responds well to increased EI. Certainly, I hate pushed TMY, and Delta 400 could be the same, but I used to love pushed HP4, and HP3 for that matter.
Ease of processing? No problem. A decent thermometer, and consistent techniques, are all you need.