I own the following DeWalt 20v tools and use one or more almost every day:
Hammer Drill
Compact Drill
Right Angle Drill
Impact Driver
SDS Rotary Hammer
Jigsaw
Grinder/Cutoff
Recip Saw
Circular Saw
Wet Dry Vac
I have absolutely zero complaints about any of them. I have three of the 2.0aH XR battery packs and they last a ridiculously long time. I have five of the 3.0aH battery packs and basically never use them because the 2.0aH batteries will get me through virtually any job.
Next month I'll be adding the 20v oscillating/multi-tool.
As a bit of a splurge, I also bought the DeWalt heated jacket. I have the 12v flashlight and will primarily use that battery for the jacket and use the 2.0aH 20v batteries as backup if needed.
All of that being said, Milwaukee's M18 Fuel lineup has more options than DeWalt's 20v and most of the tools have higher output (rpm's, bpm's, torque, etc.). Sometimes I wish I would have went with the Milwaukee lineup because they bring newer tools to market sooner and more of a variety to choose from. But I'm already vested in the 20v DeWalt line, so I'll continue to add to it.
If you like Milwaukee, I would stick with Milwaukee and upgrade to their Fuel line. They also offer a 5 year warranty vs. DeWalt's 3 year warranty.
I understand that Hilti's service is pretty outstanding. They will bring you replacement parts/tools to your jobsite, etc. But most of their tools are literally twice as much as DeWalt, Milwaukee, Bosch, etc. Assuming you will be using the "run of the mill" tools I mentioned above, I don't see the justification. Most people say you're paying more for the service. If the tool is so great and dependable, why would you need the service...?
My two cents.