If you're going to be doing architecture Viz would seem the better choice, unless the've added linking of Arch desktop drawings to Max recently. Even so in the multi 1000 price range why not go with AD 4.0 which would give you tools for architecture.
VIZ is more or less dead. VIZ Render is included with ADT 4.0, which just does the rendering, with no modeling (from what I can tell). If you use ADT and VIZ Render, you'll probably get the best bang for your buck. If you don't want the "extras" of MAX, this is what I'd recommend.
Autodesk has said that a new "solution" for the VIZ/MAX problem will be coming out this fall. Right now, the biggest headache is a lack of file portability between the formats. I think the next release is supposed to let the different programs talk to each other (major complaint since the split between VIZ/MAX).
I went from Max 2.5 to VIZ 4, only used it for about 9 months, then, bought Max 5 ("sidegrade" option). Since I do some other visuzation work, I thought it best to have Max. I also have ADT 4.0, so I think my bases are covered. I also own my own firm, and had the cash available to cover the cost of both programs and the virtually mandatory subscriptions.
If you're sticking with just architectural work, I'd look at ADT and not worry about Max. If you want to expand your 3D work, then Max would be right. Apparently Revit will be getting the VIZ Render engine, too (to replace it's Accurender engine). When this happens, I'd look at using Revit...
It's all so confusing. And I think Autodesk does this on purpose.