My vote is for the 6EA8. Heathkit adored this tube; my HR-10 had one or two, as did many of their products. The 6CH8 was some forced-loyalty attempt that is dissimilarly-based.
I have a retired TV repairman freind who replaced 6GH8's by the handful. I believe the 6GH8 was designed to save money, but tried to fill too many shoes at once. I have a late-era 19" RCA color portable that's full of 5GH8A's.
Oh, look what I found:
http://www.videokarma.org/showthread.php?t=250003