I think you might be right I have done a similar thing.
I have a ibasso DX300 but with amp 12 both the Mest mkII and Z1R cost the same amount as the Sony was second hand but barely burnt in. I gave both of them a month using stock cable and tips on both. Sold the Mest after a month. (I might try the Custom at some point but not now)
Main reason was finding a tip on the Mest was hard with the ones supplied, one would sound great say with Metallica then I move to classical and the sound was poor. Change tips, Clasical sounds good but not rock or electronic music. I do have a vast collection of tips and went through a lot of them with the Mest, comfort was great but never found a happy spot at all with the tips. If you look at the last few pages on the Mest forum Tips take up a large amount of time.
The Sony stock cable stock silicone played with the sizes and bang everything to me sounded great. I must say I think I am lucky as I find the Sony comfortable to wear.
I gave them both a good try for a month, this was not an overnight decision and it came down to this- The Sony IER Z1R made the hair on the back of my neck stand up and the Mest never did and I think at the end of the day this is what this hobby is all about IMHO
On a side note I have now moded my amp12 with the Whitigir Amp12 EX mod and the synergy with the Z1R is now phenomenal (this can be found on the DX300 forum)
Thank you all for your help in this journey.