That's before or after Bale scored the goals that pretty much brought you the double last year? Please, Bale is the superior player and the one that has proven himself for years, unlike Douglas Costa who's just starting to show up in top football. Bale is a better scorer, is faster (though not by much) and more physical, more experienced and has done much more than Costa in his career. Your opinion of course, but it really is unfounded in my opinion.
Bale has better end-speed, but Costa's Acceleration is putting Bale to sleep. Bale needs too long to enter Bugatti-mode and it takes to much field-space for that.
And thats basically the difference here, Bale wins in these Bartra-situations, where he can do a counter and cover a whole field, but how often do you see Bale having these solos in general? Like once in 10 games? Costas acceleration on the other hand is coming in handy after like EVERY dribbling and thats like 5 times a match, he is instantly on top speed and doesnt even need to cover 3 or 4m for that. 3-4m space on the wings is everywhere, he can instantly stop, turn, or change directions and accelerate again, while Bale turns like an oil tanker compared to that.
Approaching the defender, flicking the ball into open space, accelerating, see you later. Messi does that too, although with much better ball control which makes it even better.
Thats far more useful than something, that looks amazing when it is possible, but just doesnt happen more than once in 2 or 3 months.