I will quallify that comment. The main difference is line length. In BT land the vast majority of people are a lot further away from their exchanges than the vast majority of people are here in Hull. ADSL and ADSL2+ are both line length driven technologies in so much as the further one is away from their exchange the poorer your sync and throughput speeds will be. The underlaying technology is basically the same but is it that line length that causes problems. Of course, one should not, indeed one cannot, discount poor/bad/broken wiring both in the house and on overhead and underground. Nor can one discount the modem/router in use nor micro-filters in use but the main cause of slow sync and throughput speeds comes down to the length of the telephone wiring (twisted pair) between house and exchange.
Due to our ISP having a monopoly on the telephony here, especially the provision of ADSL/ADSL2+, one would think the quality of wiring would be higher. After all, they provide a city not the whole country as BT do, with the telephony network, thefore one could assume that purely on a land size basis the work involved is much lower. Indeed, it is. However, the telephoney network within the city of Hull was built peicemeal. As the city grew so did the telephony network. Bit but bit it was peiced together. This means that there is varying thickness wiring dependant on when said wiring was installed. Of course, as time progressed some of the more anceint wiring was replaced but in the main this is not so. So, today we have a mish-mash of a telephony network. This goes someway to explaining why some people are getting sub 2mb syncs and throughputs while others are getting 9-10mb and a very few greater than 17mb. The average ADSL2+ sync speed here is 10mb. In itself that may not seem too bad when compared to a comparatively distanced from exchange BT user but for here it is pathetic.
We are 1.9km from our exchange. We get a poor, for ADSL2+ 11mb sync. Throughput is 1.2MB as reported by the various download applications I use here which includes but is not limited to, SVN, CVS, GIT, FTP, Web downloads and a host of others. Our sync should be a lot higher but due to possible problems on our line between house and exchange we cannot achieve any higher. I have asked our ISP several questions for which i am waiting answers. I want to know what thickness of wiring is in use here. I want them to manually check each and every inch of it. If the quality of the line is poor I have been assured they will change it. There are many reasons why a sync could be low but by starting with the wiring between house and exchange they can eliminate bit by bit as th checks are made. I have been assured that they think the vast majority of users should be syncing between 15 and 20mb but the reality is the vast majority are not seeing those sync speeds. Therefore, they are committed to trying to establish why this is so.
Time will tell if they actually manage to improve peoples sync speeds or not.