Okay, here is my experience with the mens sizes at least. I sized up one size on the Ultra which is the "Croc" like rubber model. With the insert is is just a tad snug in length, and without the insert is it a bit long. With light socks it is perfect.
based on this I tried the Breathos and the Neo Trail. The Breathos felt nice one size up, plenty of width but the angled outer toe box side did squeeze my toes inward a bit. The Neo Trails have a heavier wrap around rubber toe guard and squeezed even more. No bad but not great either. This is simply a foot shape issue though becuase of the curve/angle of the forefoot. Another persons foot may be just fine in them.
For reference the MB Minimus MT10s are un-wearable for me as the entire forefoot angles inward. I also tried the Merrell Trail Glove in a wide size. These felt perfect with so much toe room and no pressure on the sides of my toes. After wearing the Trail Gloves around the house for an hour both the Neo Trails and the Breathos were packed up and on their way back to the dealers. Great shoes, well made and probably very usable even for my feet but when we are dealing with shoes at $100 a pair the Merrells were just so much more comfortable for me.
So, each shoe model, even within a single product line varies. Clearly the Ultras are made to a different last as they feel great while the others squeezed a little to a lot.
While not sturdy enough for real hiking or backpacking the Leming Primal Origins are super comfy. Sort of a cross between a cushy running shoe and a slipper. Butter soft uppers, a super ground feel and an ultra wide, rounded forefoot and toe box.
I know Leming has taken the difference in foot shapes between women and men into consideration and would think Vivo has too. Try a pair from Zappos or Planet Shoes, wear them for an hour inside and if not right you get free postage for the return. Most of these are hard to find in person to try on so mail order is my only option to judge fit.
Hope this helps.