This could be helpful:

http://www.bicycletouring101.com/RidingInSandals.htm

I've used the Shimano sandals, and I also have a pair of Exustar sandles that I got on sale ages ago but I never got around to attaching cleats

The problem I had with my Shimano sandals is that they are sized for men's feet. While I have normal width feet for a woman, for a man's size they're fairly narrow. So the Shimano sandal was a bit wide for me. To compensate, I tightened up the straps but that was very uncomfortable, and my foot still was a bit wobbly which was not good for clipping out. Since my husband has essentially the same size foot as me but wider, I gave them to him and he's very happy with them.

The Exustar sandals are supoosedly narrower, and they seem to be, but I haven't gotten around to actually riding with them.

Based on what I've read & my own experience, if you have wide feet, either the Shimano or Lake sandals (which have the same sole as the Shimanos) should work OK for you. If you have normal width feet, the Exustars might work out. If you have narrow width feet, you may as well just forget about sandals, unless manufactureers ever come out with sandals in women's sizes. And since sandals haven't really caught on (they're sooo fred after all ) then I doubt we'll see them in women's sizes any time soon.