I'm using some of the less expensive Getaria 2.4 tx/rc sets from Amazon, I got two sets expecting to use the 2nd set when the 1st set's batteries became exhausted. But battery life is so good I never have to switch, in typical 3-hour gigs, so I feel free to use both at the same time if desired -- I have both a piezo system and a mounted mic on my DB.
I went with 2.4 for better tx distance and better battery life. I've had no interference issues in the 2 years I've used them.
P.S. Some reliable folks here have experienced on/off switch problems with these units. I haven't experienced this myself, but I believe the reports...
And yes, I do come prepared with cables just in case. However, it is wonderful to not have any cables attached to a double bass.