By and large, there is really no comparison: HD is far superior to SD. However, that is not to say that there aren’t moments where SD is preferable to HD. SD is lower quality, but this means that it is easier to download if you have a smaller data plan on your phone, poor internet reception, or less bandwidth available. The quality of the download will unquestionably not be as good in SD as it is in HD, but there are circumstances where that may not matter.