Just tried the Mk3 and compared it with my Mk2. The Mk3 sounded warmer to my ears and there are minor improvements in the bass texture from the Mk2. I was hoping that they kept the same tuning as Mk2, but with the added midbass, to me personally, it loses the special sauce that made Mk2 really good, which is the clean and detailed midrange presentation, giving a very forward vocal reproduction. Don't get me wrong, the Mk3 is still a very technically capable set, just that I feel that it's not for me.
I think Linsoul did know this and priced the Mk3 at the same price point, because it's definitely a sidegrade, or just a different flavour. If you find the Mk2 bass too lean, then Mk3 is definitely an improvement. However, for me personally, I want a snappier bass with better texturing to match the excellent tuning on the BAs in mids. I will be keeping my Mk2 for a foreseeable future.