People say it's down to the provider rather than the hardware... Also, the image used (on e2 boxes) can sometimes affect it...
Know someone who had a really old (not sure which one) image on a h2s, was really slow, poor glitching etc. Changed it to latest whooshbuild, and made all the difference, working great.
Other thing people have to do when they are using different devices for their subs, is to try the exact same sub and channel on a PC using VLC. If the problem happens on that, then it's likely the sub that's at fault. However, I've had problems on an e2 box, but when playing exact same feed on PC with VLC, no problems at all...