Which Stick Tranny to buy??

[SRBE]

Hi all,
Im looking to upgrade my tranny/esc in my 1/10 buggy from a etronix/code digital (£70) to a more expensive set which i hope will help my driving when racing.
The 3 that i am aware of are Ko propo Esprit 4 £400, Sanwa Exzes ZZ £400 or Futabu 4GRS £240 all which come with receivers.
Some of the above or even the slightly older sets can be bought for £250ish.
So does anyone know the main differences between these 3?
Are the more expensive ones worth the extra money? What do they offer over the cheaper Futabu one?
I have held the Futabu one and it feels really nice compared to my current light/small tranny.
Any advice is greatly appreciated
Thanks Lee