I suspect most responses will be purely objective biased by subjective opinions.
Based on my personal experiences and on my equipment, the EHKT 88's trump the GL88's in high frequency extension, bass tautness, and midrange extension. The GL's do sound good and have a more balanced signature to them but seemed to be too polite on my system. If you want a no frills tube with even handed frequencies, the GL's are your ticket. If you want your music to be more dynamic, with a sense of extended frequencies, the EH88's may be your ticket. I play mostly rock, jazz and some classical on vinyl, so my tastes in music may influence the type of tubes I prefer.
Being a hobby, all I can say is that you should experiment. I am using KT120's right now and like what I hear. The 120's provide a solid bass foundation with the evenhanded sound of the GL's, but with the explosive dynamic power of the EH's. I like what I hear, they were a little dry at first, but now, music just floats in the room and there is a pronounced refinement in details that adds an uncanny realism.