In general the buffer time for HBOGo is longer than Netflix but the video quality is better.
At least in my experience, I have both
that's about what I experience as well.
if anything I get more buffering from Netflix. Pretty much every time I start a show or movie its in SD for at least a chunk of the credits. HBO for whatever reason only does it so often though like Tiger said, its for a bit longer.
It probably has to do with what ISP each person has, their home setup, what time they are watching etc etc etc.