Before I would have said archery was better, but my newest character is dual wielding and I've enjoyed it immensely also, so... it's all down to personnal preference

Both are sneaky type characters.
I would go with light armour. I just don't see the appeal of heavy armour myself (although might try it eventually). Heck, my dual wielding character is wearing only enchanted clothes now, no armour at all (was wearing armour at the beginning though). It's a great feeling walking around in clothes with just two daggers/swords. I'm playing expert, not master, and have the Lord Stone activated.