You probably mean FP4+; HP4 is an older film and any stock will be decades out of date. If you want a film to match the speed of Tri-X, HP5+ is a good choice.
First I recommend that you read Ilford's spiel here: http://www.ilfordphoto.com/products/...26+White+Films
I use mainly FP4+ and I can tell you that I get excellent results from it; it's very forgiving of exposure errors, especially overexposure. It's versatile and can be pushed to 400 ASA, or possibly higher. I find my exposures, metered with a hand-held Lunasix and exposed in my SQ-B and Yashica 124-G, and 35mm SLR, to be spot-on the 125 ASA / 22 DIN rated by Ilford - these guys make the film, they know what they're talking about! I don't faff around with 'personal film speed testing' - I'd rather take pictures! If exposed properly (meter and expose for shadows - film's exposure latitude is mostly in the area of over-exposure) the film can record a full range of shadow and highlight detail.
I develop exclusively in Ilford ID-11, which gives fine grain and excellent sharpness. Unless you're printing billboards or photographing black cats in coal cellars I don't think you'll be disappointed by FP4+. I cannot comment on HP5+ since I haven't used it for a few years.