I've been using a couple of Line6 Relay G90's for about 7 years now, and they've been pretty much bullet proof for me. That being said, I've had a number of Line6 products over the years, and the few times I've had to get support from them, it's always been somewhat of a fiasco...Enough so that I will likely not buy anymore Line6 products. I haven't used any of the newer Shure units, but I have used some of the Sennheiser G4 wireless mics and in my experience, they seem to be a little more prone to outside wireless interference. As long as the transmitter is on, the transmitter typically overrides any interference, but the minute the transmitter goes off...BAM! Spikes all over the place. Not all the time, but enough to be annoying. It hasn't been consistent enough that I've been able to do a thorough troubleshoot (other than changing frequencies, which hasn't worked), and frankly, AA batteries are cheap. If the quick fix is leaving the transmitter on versus trying to troubleshoot at a gig, guess which one I'm picking?