I like and use both. Although I so far all my usage of WG has been from the numerous samples I've gathered every few weeks or so.
When I'm buying, I'm buying Megs 21 2.0 and use it MUCH more often. Synergy perhaps.... who knows at this point. Used to be I'd use Megs just because I had so freaking much of their other products. Now however I have WG & BF in both WOWO and WOWA versions.
That being said.... I prefer to apply the WOWO versions of ANY sealant over and above the WOWA version. For me, it's a LOT easier to put a pad on the GG and apply it very evenly and very thin than it is to crawl around with a surgically clean microfiber applicator pad and just hope I get enough vapor(s) of the WOWA version(s) on the paint to actually get full coverage. (For those that have done it, you know what I mean. A few drops on the applicator pad and wipe an entire panel, few more drops and another panel, (reminds me of lather rinse repeat).
I just find it frustrating to get full coverage with what it literally vapors compared to a film that I KNOW is there.