hp= horsepower to the crank/flywheel
whp= wheel horsepower, power directly from the wheels. there is a loss in power due to drivetrain.
whp is what you want to look at for best readings on the actual hp.
ditto. you should definately pay more attention to whp than bhp.
and example would be the celica gts and the acura rsx-s. i've said this plenty of times already but i'll say it again:
factory rated horsepower (they use bhp, naturally) for the gts is 180 bhp. for the rsx-s, they get 200 bhp. so just by comparing these #'s you can assume the the rsx-s does a lot better than the gts because it has '20 more horses'. (just for the record, the rsx-s does put up VERY slightly better #'s than the gts, except in 0-100--which the celica is better.)
but anyway, when you dyno a car (dynos rate whp), you can see some dynos for the rsx-s will come out to 163 whp. dyno a celica gts and your average output will be about 160 whp.
so now, that '20 horsepower' is really only 3 horsepower--NOT a big difference.
bhp is what the engine is capable of producing without the friction of the drivetrain, etc.
whp is what's left after all that lost power is subtracted. hence, it is the better number to go with because it's actually what you get to drive around with.