I have a variety of shoes with different levels of drop. My fell shoes of choice are on Inov 8s 2 scale, which is 6mm differential and think this is about right for me (ATM). They make my Adidas Kanadia’s feel wallowy.
I have a pair of Merrell trail gloves which I did 10k in the other day (1st proper run in them) and the outside of my calves are a bit sore now (3 days on!).
I will replace my Adidas Kanadia’s with some Inov8 Roclite 330s (9mm) for my trainign runs. This is driven by the need for a bit more padding and durability than the fell shoes, but also less differential than the Kanadia’s.
I don’t have any aspirations to go to a 0mm differential as a matter of course, just working with what feels right. I’m using the trail gloves to build up other muscles – a supplementary exercise to reduce injury.