it all depends on whats comfortable for you.
i like a medium to low rise, and one mate likes a high rise and another can't see past flat bars.
the lower the bar the more weight you have over the front of the bike, same as a wide bar (though wide bars also help get rid of a twitchy feeling front end). and the higher the bar the more weight you have over the rear of the bike.
if you can, try different rises untill you find the one that suits the way you ride best. you may have to ask mates for a borrow, or if you get on well with your lbs they may let you try some bars for a quick ride in the car park.