so adsl2+ gives you better up and down stream margin then G.DMT ?
No, not at all. Just the opposite. The faster you go the more stress and demand is placed in the entire line and even more so on the inside wiring.
ADSL2+ drops speed dramatically as distance increases since the ADSL2+ places 4 times the load demands on the line.
If you have a Marginal ADSL line that get less than 1.0, then you are not going to see any miracles from ADSL2+.