The 8800AXL VDSL modem is Broadcom, and this is very much the same performance as the BT supplied HG612 which is also Broadcom. There are different versions of the Broadcom chip, but essentially the modem part is exactly the same.
What can cause differences is how good the overall design is of the external components and circuit design, although these days the gap has narrowed and the 8800AXL seems well designed. The other thing is consumer modems aren't designed to last, after 12 months of 24/7 operation they can start to degrade, so the noise level rises and that can reduce the sync speed and or SNR margin which can cause an increase in errors, not necessarily by much, but just getting a new "anything" can see an improvement just for that reason alone, its new.
So at worse, you'll see no differences, at best you might gain something on the line sync speed.
Other advantages are you swap two boxes for one with an all in one VDSL router, so save a bit of power and a bit of space. There shouldn't be any difference in ping or speed differences assuming the line rate stays unchanged, unless of course your current router is struggling.
Edited by PhilipD (Mon 30-Mar-15 08:30:51)