Im looking at getting the sl or the legacy, how much wider is the legacy than the sl, im 5'8'' 165 to 170, with a size 10,
You really can't go wrong with either. I have the SL wear an 8.5 so I don't have to worry about toe hang. Not sure on the exact specs of the width. try contacting a gear head directly, they've got all the answers!
With a size 10 there's no reason to get the Legacy, the regular SL will be fine. I wear a 10.5 on my SL and I've got tons of room to spare.