Need help with picking a soccer cleat size.?

I wear mens 10.5 US size shoes. I bought some Nike Maestri's size 10 online via ebay and I got blisters on my heels and toes from wearing them. I found another pair of cleats online in both size 10.5 and 11. Which one should I get? I dont know if I should play it safe and get 11's or go for the tightest fit possible and get the 10.5's. Any help would be appreciated.