Got my 4x10 back to my Chamonix 45H--1 a month back or so.
So I'm just started on that format. 4x5 was my largest before.

So why did I not go to 8x10, as some suggest. It's indeed more flexible in many ways... but...

- 8x10 would mean I had to invest in new drums or trays and space for development. With 4x10 I can use my current drum with only a small adjustment to my sheet film holder.
- 8x10 would mean a new scanner, probably a Epson flatbed instead of my current Imacon Flextight with a 4x10 holder. A flatbed would not produce on par with the flextight on 4x10 in my opinion (And please, let us not get into a scanner debate here )
- A good 8x10 camera would cost at least the double compare with the Chamonix 4x10 back (as I already have the 45H--1).
- It's still portable, and fits in my regular 4x5 backpack.

So it all depends, just making a case for 4x10.

In my case a 6x17 back on a 4x5 or 5x7 would have been an option. Shooting on rollfilm is very convenient sometimes. But 6x17 has always felt a bit too wide for me. 4x10 is more balanced as a format I think.