It's hard to find an army that dominates in it's magic phase as much as Beastmen do. Shard of the Herdstone and cheap level 1s guarantee 3-4 power dice before channeling, jagged daggers allows you to get more than 12 power dice per turn as you turn in models that have been killed by it's bearers when you need the power dice. Then you have all those level 1s throwing out miasmas to make your troops hit harder. So lets compare them.
Beastmen
-Primal Fury,
LD based hatred rolled every round of combat, failed less then 5% of the time with Ld10 and
BSB rerolls
-Bestigor and Gor are WS4
-Bestigor hit just as hard as Iron Guts at S6, no stomp or fear though.
-Lore of the Wild sucks but death, beasts and shadow all work well with Beastmen
-Doombulls, enough said
-Chaff Chaff and more Chaff, 30pt ungor raiders, harpies, razorgor are incredibly good
-Pretty much no shooting, sorry ungors BS3, S3 just doesn't cut it when you are firing off 5 shots
-S3 gor suck but can be fixed with magic augments and beast banner
Ogres
-Stomp and Ogre Chage
-Mourfang crazy good, good armor should crush most units
-Leadbelchers are better
-Ironblasters are crazy good
-WS3 will make you pull your hair out as well as I2
Ogres were my first army, I love them fattys but this was prior to the new book and the WS3 made me sad, so I started Beastmen and the jump to WS4 with rerolls was really nice. The more I bought and the more I looked into and played beastmen really became more awesome to me. I also like they were the last army of 7th built with 8th in mind (see
LD based Primal Fury and
BSB rerolls) and they aren't stuck with the mandatory 10pt unit command that all armies in 8th have. As for rolls I have seen beastmen competitive in mainly 2 builds herdstone spam and minobus but there are other tactics, if you are familiar with Brettonians you may have seen Oncebitten360's videos on you tube and he plays Beastmen as well with a cool scheme where he uses minotaur to deliver a doombull that just wrecks everything, his most recent video (
http://www.youtube.com/watch?v=wBjqnJYUjAs skip to about 15:20) watch a doombull take on a gutstar that gets the charge off on him, albeit he had some really good rolling.