You might want to repeat this over at WildGuzzi.com, but here's a general answer for you.
The singles were never imported in any great number to the U.S., so even if they're fairly common in Europe, they might be a little to obscure for you. I'd love to have one, though. As for keeping up with traffic, it obviously depends on what your traffic looks like. High speed commuter freeways? No.
The twins are more alike than different all the way back to the first V7. But, if you're looking for a sportbike, a Mark3 LeMans would be a good reliable mount to work on (and could be had cheaper than the more desireable Mark 1 LeMans or V7Sport). The old loop frame Eldo would probably be the top choice of the standards. There are lots of them out there, and they are a good handling, very reliable bike. I'd stick with an Eldo before going to an older Ambo. If you want to get more weird, how about a Convert with an automatic transmission?
And, I guess you could look for the same bike that I have had since new (The California 2, not the Daytona). It's now 20 years old, but it's about as reliable a motorcycle as Guzzi ever made. They can be found for around $3,000 for one in pretty good shape. Finding parts is not a problem.