I'm finding I'm using the 14" MT and Nela Black flexi more tbh. Although just done a ceiling yesterday over stippled artex, put on with the 14" MT and used the 16" Nela to give it a flatten between coats and first trowel, switching over to the 14" Nela Black flexi for 2nd trowel. Polished off with the 16" to break it in more. I find the Nela Black Premium Elite a nice comfortable trowel to use as it doesn't rag my knuckles like the MT. Pity I didn't get the 14" version instead of the MT (although I bought and used the MT the same morning as I needed a longer trowel for a staircase job where my 11" didn't fit behind the floating treads)
I don't think I'll be buying anymore trowels otherwise I'll end up not using them all.