In a regular shoe, I usually wear a 9, sometimes 8 1/2. When I got my
Crocs Mary Janes last summer, I was torn on the size. The 8's touched my toes on the end, but the 9's seemed too loose. I got the 8's, and they stretched and fit beautifully. I lived in them all summer.
When I got a new pair a couple of weeks ago, I got 8 again without even trying them on. When I got home I thought, uh oh, these are touching my big toes. So I wore them around with thick socks for the morning to stretch them a little, plus pulled the back strap out gently. Now they feel great.
On the other hand, I've read a number of people say to go up to the next size with the MJ's, so maybe it depends on how you like them to fit? Maybe either size would work for you depending on how you want them to feel.
BTW, except when stretching them, I usually don't wear them with socks because my feet slip around in them unless the socks are thick. Without socks, the shoes kind of grip my feet, which keeps them from slipping.