gwarsh41 nailed a lot of the advantages on point.
- You get 2 special weapons per 10 men, instead of 1 special and one heavy
- You get extra options for the squad, like a power fist.
There are also some drawbacks.
- Counter assault is a poor trade for Chapter Tactics and Combat Squad.
- Wolves do not have access to telepathy.
There are some cool combinations you can with wolves.
Ulrick the slayer spaced carefully can give a big chunk of your army preferred enemy. If you run the numbers on preferred enemy, you will find that, on a BS4 model, its slightly better than being twin-linked when not snap-shotting. Given the lack of psychic dice to make this buff happen, its pretty sweet.