The only numbers about bitrates I've seen comparing D*, E* and V* are these (compiled by Mike123ABC on DBStalk):
"DirecTV uses the most compression on their HDTV channels of any satellite provider.
DirecTV HDTV is 15.8Mbit, vs 16.9Mbit on Voom. Dish is 19.8, just like the OTA HDTV channels.
(Details compiled by Mike123ABC on DBStalk:
VOOM Runs 8PSK 22msym 5/6 FEC 188/204 RS or 50.69 mbit/sec or 16.9mbit per channel with 3 HDTV channels (minus some because of guide data, etc but not much).
DIRECTV runs QPSK 20msym 6/7 FEC 188/204 RS or 31.6 mbit/sec or 15.8mbit per channel with 2 HDTV channels
Echostar current is 8PSK 21.5msym 2/3 FEC 188/204 RS or 39.6 mbit/sec or 19.8 mbit/channel with 2 HDTV)"
source:
http://bbrcs.clanspace.com/forum/remark,8721971~mode=flat~start=20