2H > DW
Not being able to block or power bash leaves DW defenseless.
With 2H you can use and I recommend the following perks from the Block perk tree:
- Shield Wall
- Quick Reflexes
- Power Bash
- Deadly Bash
You can also pick the Disarm Bash perk, but I don't find it that useful.
It is not quite true. Dual-wielding has got a higher attack rate. You do not necessarily need to be able to block when your attacks come faster than your opponent's and their's get interrupted.
With two-handed do you need to block, wait for your opponent to stagger and then hit them. In the same time can you do dual-wielding power attacks and simply break through them. It is not tactical at all, but it kills.
I kill ancient dragons on Master with a daedric sword and a daedric axe, both enchanted, by 2-3 power attacks. I need one power attack for most other opponents. There is no room for anyone to block anything, really.