its more that the power cutback on vdsl (to protect adsl) makes vdsl worse on longer lines.
If a vdsl line can only use the adsl frequencies then it will be crippled as it has limited power on those frequencies, so then adsl works better, but of course adsl may be on a longer distance due to been from the exchange instead of the cabinet.
It seems when a cabinet is close to the exchange the power cutback isnt that severe and on frequencies above the adsl1 range, but when its far from the exchange (like mine) the power cutback almost completely wipes out the low frequencies. When I compare bitloading graphs posted from unlocked hg users (most who seem to be on cabinets close to exchanges) my estimate is about 8mbit/sec of attainable sync difference depending on which power masking you on.
BT Infinity 2 Since Dec 2012 - Estimate 65.9/20 - Attainable peak 110/36 - Current Sync 71/20
Edited by Chrysalis (Wed 06-Feb-13 00:00:21)