Much of a muchness I suppose. The Billions seem to have a good reputation... but the one thing that made it unsuitable for my requirements is that it only has 1x GbE port and 3x 10/100 LAN. Because I wanted to get rid of my gigabit switch it wasnt a viable option.
The VMG8324 has more hardware ie 4GbE LAN ports & 1 GbE WAN (can be used as 5xGbE LAN). It also has 2x VoIP and 2 x USB ports... plus it also looks sexi on the desk
The Web GUI is one of the best Ive seen.. but there is so much in it that it can be confusing for the more novice type user. A lot of functions that would normally require CLI commands can be done straight from the webGUI. The downside is the webGUI appears to have a couple of bugs - ie the save function doesnt always stick first time for some people... and the login button can take a while to appear. It has its quirks, but then again all of the VDSL2 units seem to have some downsides and I dont think Ive heard of one yet that is 100% perfect. Now Ive set my Zyxel up how I want it.. I dont need to touch it so for me it just works.
Its fair to say that Les said he saw more errors with the ZyXel.. but its not anything that Ive noticed on my line when compared to the HG612. So I guess its one of those suck it and see things