Swift-Fit Slip-On Sneaker

I love these Slip On Swift Fit shoes but I'm finding out they're not all alike. Even if they look exactly alike they can be different. For instance with these, even though I ordered the exact same size as another pair I recently bought that looks identical to these, these came in a half size smaller. So, I sent them back and orderred another pair but this time a half size larger than my other pair and they fit exactly the same as that pair. The soles on these are also a little harder than my original pair which I don't appreciate at all because I prefer the softer version. It's more than a little annoying that there's so little consistency in size and comfort between pairs of shoes that appear to be exactly the same.