I have a Milwaukee M12 Surge, M12 Fuel Impact, Festool TID18, Festool C18 and Bosch Flexiclick (brushless).
The TID didn't impress me at all, same run-out as Milwaukee, not the most powerful of the 18V Impacts. It has good ergonomics and it's not too heavy.
M12 Surge is fantastic, not as strong as an impact, but great for any kinds of screws, since it sustains the torque for longer periods. Also super quiet for what it is. When I have to use my impact, I always regret not having the Surge with me instead. Also the M12 Surge has the same power as the M18 surge. And last thing about the surge is the feeling when driving screws, it doesn't feel like a standard impact, but more like regular drill. It's hard to explain, but it's about the feeling not the noise.
M12 Fuel Impact has exactly the same dimension as the Surge, it's a standard Milwaukee impact- a lot of power, good ergonomics, 4 driving modes. It's way louder than the surge though.
C18 is a great drill with many different heads and good power. It sucks for screwing though. It's super heavy, and if you are screwing into hard stuff, it starts skipping in the end, just like any regular drill. I mostly use my C18 for drilling, it's great for that.
The Bosch Flexiclick is amazing too. Very short and light, way more heads than CXS, lower price and way more torque. I used it with 4" construction screws and it has no problem driving them.