I did read this post and totally forgot to answer!! My apologies.
ChazzyP is correct. I have used the iMamba as well as CRK’s on the job. I have also owned multiple Shiro F95’s, Neon Zero and Neon NL.
Not sure if any of this info will help the OP or if they have already made a decision.
Between the AB iMamba and the Shirogorov Neon Zero, my choice would be the iMamba. They both have roughly the same blade length. The Neon Zero is a slimmer knife and is, in my opinion, not suited for the tasks I make my CRK’s perform in the construction business. The Zero to me is a light duty flipper. I did end up selling it, because the tab would get in my way in different grips, and the Zero was just too slim causing some discomfort in cuts requiring a lot of downward pressure.
The iMamba I have in both a washer version and a bearing version. Both have stood up very well and have been put through some pretty tough tasks. As you can see in the photo, AB’s finish hides scratches in photos well. Haha. They are scratched up though.
Both of these came with a flipper tab, and were used that way before I performed flipper tab delete surgery. (Just a personal preference). I like the way the flipper tab was positioned as it stayed out of the way for 90% of my grips. It’s got great action and feels very much like a CRK in hand…just a touch more comfortable ergonomically. The bonus is that the edge is easy to touch up with basic sharpening systems.
Between the two, I would decide what you would like the knife for.
Shirogorov Neon Zero for incredible action, thin profile and light to medium duties. Great machining and attention to detail.
AB iMamba for great action, good ergonomic handle, satisfying purchase in hand, ease of sharpening and excellent machining.
Not sure if this helps, but I had fun typing it out.
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Edit to add: A fun fact. Your middle finger is the longest finger on your hand. Your brain knows this and it is intuitive. If you were to measure your middle finger, that would correlate to what blade length would feel the most natural to use the second you pick it up. Your brain is used to the distance so that blade length feels natural.
It took me a bit to get used to the 21 being just that little bit longer than my intuitive length of 3.25”/3.30”. In fact, I sold my first 21 because of that, it felt a little to awkward. I bought another 21 and it was maybe 2 weeks to get used to the length.
Just a fun little fact to consider.