I am with Iddee. I like the idea of bigger brood areas, but with a bad back I am seriously considering moving to 8 frame equipment (will still use deeps and a mixture of mediums and shallow for supers). Plus, when doing inspections you might have to re-stack 3 boxes instead of just 2 - that is just more bees getting smooshed :(. I do like that with deeps and mediums I know which frames might have had terramycin or other treatments dumped on top of the frames and that all my mediums or shallows are dedicated to honey collection.
I guess if you make your own nuc (which you may well want to do sometime, if nothing else from a caught swarm, or managing a split or a bunch of other reasons), you could just do it in a 10-frame or 8-frame medium, which I have done, but I like the idea of a 4-5 frame deep nuc for these purposes. I always keep one of those 5-frame deep cardboard nuc boxes handy for a swarm collection or split or transferring brood frames somewhere. Awful handy and light - easy to carry without having to deal with separate bottom board. I don't think anyone makes medium cardboard nuc boxes, but not positive.
So, I still think that an 8-frame deep offers best of both worlds.
It is moving those supers that is the biggest job - you often don't go far with your deeps (unless they are empty :'()
You use a frame for brood and they fill it full of pollen and then using those frames for supers is not ideal by any means - so frames aren't always totally interchangeable.
Three mediums cost more than two deeps.
Most treatments are measured out for deeps.
Most nucs are sold in deeps.
Most damage to backs is done during bending, rather then carrying. I would rather lift and carry one 60 lb box "2 bends" then 2 trips at 45 lb each."4 bends"
I have removed many colonies of ferals and have never seen horizontal bee spaces in the middle of the combs, like different boxes give, so I like to use a minimum number of breaks in the comb. That's why I used all deeps when younger.
Also, with a two frame extractor, I would rather extract 20 deeps than 30 mediums.