I run them and they are rock hard. Bashed them enough times and cased a few landings etc and there be nowt wrong. I would recommend the X-type cups too if your a big bloke- doubles the load carrying ability of the bearings (apparently, probably doesn't double it but it'll help). I'm only like 10 1/2 stone but the setup is overkill for me really but it came as stock on my bike. I reckon it'd be good for you. What about Saints though? Don't know about them myself but 'the last crank you'll ever buy' is often said about them.

Well I'm about 14stone and have had the isis evolves for over a year now, and they're still going strong
They were on a hardtail for about a year and took quite a beating but still come back for more

I'm running RF Evolve DH X-Types on my Demo 8. Rock solid cranks but the BB bearings are rather cr*p. Good thing is that Shimano Saint/XT external bearings fit and last alot longer so worth the upgrade once the RF ones die (which they will...).