The form factor is worth something. It's the reason I bought a Seabear H3 and then sold the Petrel 2 that I had.
No way you'd wear an iX3M to work (in an office setting). ;-)
If my H3 died, and if the Descent gets an AI upgrade (i.e. Mk2), and if the Descent actually works well for deco diving, I would definitely consider one as a backup to my Perdix AI. I much prefer the smaller watch-sized form factor over the big, thick Perdix form factor. My H3 is watch-sized and it is just as readable as my Perdix. It doesn't show quite as many pieces of data, but it does show all the ones I want.