Just about every contractor around here (USA based) is using Milwaukee, Dewalt or Makita. These folks make a living with their tools and don't have patience for junk. Even lower tier brands like Ryobi are more than capable for home use. I got a lot done around the house with a basic Hitachi drill and corded Skil saw before treating myself to some fancier stuff.
I've yet to meet a contractor who's brand loyal to the point of only using that brand. Most have two or three brands they tend to go to.
As for brand loyalty - it comes from the fact that batteries are more expensive than the tools. A handyman or a two people crew on a small job can have five different batteries with five different charges for ten different tools in the truck without much problem. A crew of ten people working on the same site for days will need multiple batteries per tool and if they try to use different systems they will end up with people waiting for a free outlet so they can charge and work for a couple more hours before they will need to wait again. It's much easier to set up one charging point and pool charged batteries for everyone to use.
Lots of the super price brands like Festool are more ... showoff I almost feel.