A difficult choice indeed.....
My GT is nearing completion, so I don't yet have an 'on the road' comparison.....but being fortunate enough to have one of each I'd say the GT40 wins hands down every time. I love my Strat, but the GT40 is just something else. When it fires up there is nothing quite like it! I can't wait to get it finished and on the road.
Good luck with your search. As you say, there's a lot more to choose from with the GTs. You should definitely think seriously about Tornado. There have been many manufacturers come and go, but Andy at Tornado has been there for the duration and personally I think this speaks volumes (when I met him at Stoneleigh he said he had built several hundred cars/kits now). I have always found him very helpful and approachable and you can pick up the phone and order parts, and know that you are going to get them (my cars not even a Tornado!). I'm not sure where you are located, but it would be worth paying him a visit to talk through his product.
Good luck with your search.