If you can fence it off into small paddocks and do rotational grazing I might leave it stand and graze it.

If you intend to turn the cows into an area that has enough grass for them to eat for several weeks they're gonna walk most of it into the dirt. 

In that case I'd bale it off and let it regrow for as long as possible before turning them in.

Worst case scenario is you have to feed some of it back to them.       Also, a bale ring is about the worst possible way to feed hay to cows.    Only slightly better than setting the bale on the ground without the bale ring.

Unrolling/shreading hay in windrows only putting out what the cows clean up in a days time is much better in a bunch of ways.