"adls max needs a pristine line, while adsl can work on noisy lines"
Actually, the opposite can be the case (not saying the Openreach engineer didn't know what he was talking about, because his training would have prevented that from happening, but he may well have been referring to the abilities of ADSLmax to work at high speeds).
If a line is too noisy for the chosen fixed speed package to hold sync, an ADSLmax product may be the solution, as it will naturally find the highest speed a line is stable at (excluding a few system 'bugs' which can prevent the automated process from working correctly, or accidentally triggering it when no real/permanent fault exists).
Ade
Giving UKFSN/Entanet a try
DL Sync 4600+ (now 2464 and screwed up by pointless 15db SNR target)
UL Sync 448