HuffYUV is a way to get RAW captures compressed without losing any quality, because it won't throw away any information.

MPEG2 is very very good, but it does throw away some information in order to compress. 15mbps capture rate is huge, this will give near perfect quality captures for sure. Bear in mind that your Sky box itself is compressing to something like 8mbps MPEG2 if not less, because the transmissions themselves are in an MPEG2 hybrid format too, so they are already compressed...