Since you already pointed out the obvious go to a bootfitter and let them fit the correct boot to your foot by looking at length, width, ankle mobility, skier ability, arch height, foot shape, and a million other things that you cant do at home, il save you that lecture. But seriously, go to a bootfitter please. You wont regret it.
To actually answer your question- Theres a couple things that I can answer off the bat. The Cabrio and Diverge are both three piece boots. They have a different flex pattern than 2 piece (overlap) boot designs. Its possible to get a good performance out of both of them, and yes some people prefer the flex of the 3 piece over the 2 piece, but the decision should be made by what boot the bootfitter puts your foot in. Take a look at this thread for more info on 2 vs 3 piece:
https://www.newschoolers.com/forum/thread/936221/POLL--OVERLAP-OR-CABRIO-BOOTS
Another thing id like to point out- how much do you tour? Out of the three boots you listed, the k2 diverge SC is the only boot with tech inserts, which is very important if you see yourself getting a touring setup or upgrading to CAST at some point. (hint- you will regret not having tech inserts sometime in the next 10 years). The Dalbello Cabrio Free is Dalbello's hybrid version of a Cabrio.
The boot that I use is the Tecnica Cochise 120/130. I love it, but I also saw a bootfitter and will only recommend it to someone whose bootfitter also recommended it to them.
