Yes I have, but only informally so far, with no metering equipment.
Seriously though, for a first can purchase, I would recommend a full size can over a reduced sized one. The difference between a full sized and a reduced size doesn't seem bad to the shooters perspective in an open environment, but is very noticeable in smaller spaces. The smaller ones are great, but it's a more specific application.
The tones are different between the manufactures, but actual db haven't been measured in my cases.
One thing that sticks with me personally is that the offerings from both have great flash hiders, but different brakes. The KAC brake is less disruptive compared to the SureFire by a large margin.
I'm happy with both, but I prefer the KAC offerings more than the SureFire so far. So far, both have great consistency and lock into position well, and have repeated accuracy so far. The Surefire cans seem louder on subsonics, but I haven't measured it. The attachment method is super easy for both.
I use silencers on multiple host weapons, so I like being able to make them usable for a wide variety of platforms. If SureFire made a less nasty brake, I'd say they are close.
Hopefully, I'll be doing some sound testing soon, it seems almost impossible to get everything scheduled.

