I own both.
The G10 came first.
If I had all my effect pedals or my Kemper Stage (or any other all in one system) permanently fixed to a pedalboard, I would use the G10. No doubt.
As I use an all in one system that uses to go in a cabin case, I prefer the WL20. No doubt. Much faster to set up and pack. Much more. And cleaner area and less footprint.
So I have the G10 living his golden retirement at home, always connected to the system I use there, and take the WL20 on the road.
Both sound very good, BUT, I find that, having the receiver on the floor, the G10 works better; the signal travels better than when I connect the WL20 to the pedals. I solved this getting a 1.5 metres guitar cable. I connect one side to the Stage/AX8/HeadrushGigboard and the other side, after fixing it to the microphone stand with a rubber band, to the receiver. No problem, then, no matter how big the stage is.
I think I must say the G10 transmitter recharges the batteries surprisingly fast.
My gigs are 2-2.5 hours long, and I can do 2 gigs with their soundchecks with any of the systems without any problem. Probably 3 or 4.
I also had a Line 6 G30. It was my first wireless. Fantastic, but I like much more not having the transmitter and a cable in the guitar strap. And now I don't have to worry about batteries, (that's a very very important plus for me and, supposedly, for the planet).
So, short story here:
Considering that both units have great quality:
-If I use a pedal case with things permanently fixed to it, and there is room for the G10 receiver, I'd go for it.
-If I'd just use guitar and amp, or and all in one pedal system (or different pedals to set up and pack every day) NOT fixed permanently to a case, WL20.
And, well... Finally answering your question () : I think both systems sound better than a regular cable.
Hope this helps.