All FWIW -
I've learned that is impossible to buy a bike "by the book" (or by the magazine
) - that is, other people's reviews may turn out to be different than your experience. I once bought a brand that "everyone" said was the best bike they had ever ridden. They were right - but they were right for them. I didn't "gel" with it, it was a smaller platform and the suspension wasn't up to par. That's OK - I was out to find the "best bike" and I learned something in the process. That one didn't "feel" right. When I rode the 2018 GG, I found the bike for me.
So if you like your GG, I'd encourage you to find a way to ride those other bikes before purchasing. If you can't, then if possible wait to sell your current ride until you've been able to compare it with the new one in back to back rides (careful though, I've done that and have yet to sell my 2006!).
I admit I have not ridden a Beta yet (only Sherco and Husky TPI). The Betas look great, and would be high on my list - but appear in the showroom (and from the reviews, which I just said to take lightly) to be a slightly smaller bike, which is good for some people and not for others. It's also possible that Beta suspension (whether KYB or Sachs) may need some work to match the action of your current GG suspension (which I find to be great!), but that may depend on your riding style. Can't really know until you try though!
All good choices, and all good fun!
Jeff