or, which band YOU are using that works incredibly well for you at least.
The THREE of us in my band with Senn G3's have the "G" band.. based on data provided for our area by the Senn frequency finder
http://en-us.sennheiser.com/service-support-frequency-finder
That was my post on TB (if you hadn't figured that out!)
What I (we) did was to look at the results for Dallas, TX (which is where we are based).
If you look at the 2nd image of that post, there's a lot of "green". Those are unoccupied frequencies. In other words, using frequencies that are "green" will minimize outside interference from TV stations.
G - band is 556-608 Mhz. It's almost completely open (green) in that frequency band.
A - band is 516-558 Mhz. There's one TV station in that band..
B - band is 626-668 Mhz. There's 3 frequency ranges in use by TV stations in the area.
You can also look at the TV stations transmission power (Kw) and the impact radius. If you are outside those ranges, you will get less interference, maybe none. Best to avoid them tho'..
You will NOT get interference from smart phones as they use 2.4 or 5.0 Ghz ranges for wireless. In making my choice I also checked other zip codes in our area to see what came up. The "G" band was the most open. We went with those.
I have had ZERO interference since going with the G3.
Depending on your locale, YMMV!
PS: There's also a way (if forget if that's on the Senn site or what the URL is) that lets you enter a venue address. It then displays the transmission direction of the local TV stations factoring in Station transmission output to estimate wireless impact in your chosen band at that location.
Note that is you have multiple units working, you WILL need to ensure that each unit is on a different frequency, or you'll be hearing someone else's mix!