They are stronger as far as I know, but they're also a lot heavier. Which is fine for a DJ/street bike, but for general purpose freeride with maybe a little XC, aluminum cranks and a good bottom bracket should be good enough.
Profiles are probably one of the most durable cranksets around, although one of the DH cranks with ISIS BB might come close.
I'm not sold on bmx cranks, mainly because I tore through three bottom brackets in like 2 months. They were Euro style, so I guess American would hopefully be stronger. I ended up going with evolve dh cranks with the external bb. A bit heavy but, damn, I love them. So smooth. There's even a few mm chainline adj with the spacers.
BMX cranks are mega-stronger; and heavy too. Most run a soild (or near-solid) BB spindle with a 48-spline BMX pattern. FSA makes one too. The crank arms are hollow chromoly and shaped like an aluminum arm and the BB is a solid 48-spline with three bearings (two on the drive side). But, really, it's overkill unless you're Bender...or weigh 250# and kill everything else. The Holzfeller's should do you fine, or look at the FSA Pounder.
To put the weight in perspective, Profile cranks with a euro bb will add about a pound to your ride, that is if you had weenie-light cranks installed at first. Most people that freak out over the weight don't consider that the profile system includes the bb and spindle.
A set of euro bb profiles without the spider or rings weighs about 1100g.
A set of typical MTB crank arms with rings plus a BB weighs in about 900g.
Figure once you add a spider and rings to the profiles, it'll add a little under a pound to your bike.