grab an anatomy book ;) the new pose is definitely better for rigging and skinning and also for modelling but you shouldunderstand how the bones are built and the muscles are constructed around them, even though its stylized, that knowledge will give you a way more believable result.
the elbows are kinda floppy and the forearms look popeye, but not in the cool kind of way, but in an accidental way. The shoulder/bicep area looks kindof weird like someone just took a clay tube and smashed a part of it. No real anatomy going on here. Perhaps you're going for a style - if so post your reference?