I've had Vetos for 12yrs cannot beat the quality/5yr warranty and being able to organise the tools like they do
XL 6 years daily use in Electrical work mostly industrial
Personally I've had over 25kg of tools in mine with no problem except I was lugging stuff I didn't use all the time it had more capacity than I needed so I filled it up with stuff I rarely used
I chose the XL because the sides fold and secure down when your working and can be closed up when moving around or if its raining or dusty
Last 6 years I've also used an MC and a MB meterbag as I changed job and didn't need hammers hacksaws etc all the time as it was more control wiring on machines so some smaller electrical/mechanical tools required and I wanted something that would fit in a suitcase for overseas jobs
Even though its smaller I carry 13kg of tools which if i had to replace tomorrow would cost around ÂŁ1200 , therefore to me it makes sense to protect them properly.
I wouldn't aim for too big a bag as you might end up carrying stuff you never use, better to have more or less the most utilised items in the bag to hand and other stuff in the van
If I was to go back to general installation work I'd be looking at the LC or possibly even the smaller backpacks if on large sites.
Plenty of YouTube videos showing their capacity, I would say it depends on how much you really need to carry, how mobile that job is and what the environment is like