As topic .....
I usually use the bucket style for installs and the bag style for service. Either one can get heavy if you start to overload. Just don't wear out your back ;)
I use another tool box for air conditioning tools and one for plumbing tools as well.
One thing I learned if you're buying tools, like a ratchet set, or a drill, or even a toolbox, never buy one that has a case with plastic latches.
https://www.google.ca/shopping/product/5050683515859593945?q=milwaukee+bag&client=ms-android-rogers-ca&sa=X&biw=360&bih=612&tbs=vw:l,ss:44&prmd=sinv&prds=epd:11001906483763718643,paur:ClkAsKraX1jcao4DebtIvCQgOdil9WI10ijKruBzYiQJ4Obq8IsHMgw6kEf7g97EATg20PNavIP4BbLnGK3-3DiaEO8UNV9GJbbEtN-bcJkQAErGsJHtcAV3GBIZAFPVH72xhqScDXW8gB0FkMej-brBKE06pQ,cdl:1,prmr:1,cs:1&ved=0ahUKEwidmPfi_8jeAhWR7FMKHaHUCFwQgTYIvgQ
That would be alot easier on the back. Not cheap, but worth it!
Used all of them except a backpack. (I don't want to feel like a high school kid standing at the customers front door).. My favorite is the 20" pro husky tool bag. It has a nice slot on the side for me to store my 18" bar folder. All the right pockets and sizes for all the various tools I use for installs and service. I like how the center console just slips out and I can have easy access to other items below. It's just big enough to hold everything I need. The center console might be tough for guys with big fat fingers to get into, but you can remove some of the slots to make them larger.
I often used the bucket style ones in the past, but I find I always needed to shine a flashlight to the bottom to find tools and fittings, and had to the tendency to let it fill up like a garbage pail with things I don't need.
I use a Veto Tech XL for my furnace and A/C service calls and Veto Pro Pac for my water heater calls.
The tool backpack idea came from being downtown and having to park blocks away.. Made it easier to walk around with it on my back. For in and out calls, a tool bag would be more convenient.
Depends on your work. Service tech vs installers, residential vs commercial, urban vs rural.
https://www.amazon.ca/Custom-Leathercraft-1134-Backpack-48-Pocket/dp/B0047O3PFC
I love the tool bag