for me, i love high speed film. more versatile in my opinion.
i have 20 rolls of PRO 400H in my freezer. it's good stuff, very natural colours.
with any negative film, it is always better to overexpose than to underexpose because you get some more grainy shadows. however, i did a few experiments with 400H deliberately underexposing a stop and the results weren't too bad.
400H is a very popular wedding film because of the more natural colors. as well, if you deliberately super overexpose, you can get a bit of a dreamy effect.
a few of my test photos, first 2 are +1 EV and i think the last one is -1EV