Annual grows much faster which means you'll be mowing more often. I prefer perennial, but it's almost twice as expensive. Then again it means less mowing.

If you want to mow in the winter, go for it! That's one reason I enjoy winter - no mowing! It's really meant as a cover crop or forage for wildlife/livestock so it normally gets clipped by being eaten. It will also die as soon as it starts getting hot.

I grow patches of winter triticale where I have annual beds, but don't cover my whole yard with it. It's a great weed suppressant and the seed heads dry really well for crafts.

Just a thought. Deer hunters sow rye grass in their hunting fields for the purpose of ATTRACTING deer. Chances are your lawn of rye will do the same. Trust me. You don't want to borrow trouble. Once the deer find your garden, they remember where it is and invite all their friends! :)