I don't even see how the Sportster fits in that comparison, other then the retro looks and low technology, which I definitely see as good. But aside from that, the Sportster is a much smaller bike. I just don't fit on it. I haven't tried the Guzzi, but I have sat on the Bonnie, and it has a LOT more room than the Sportster. I really like the Sportster, just wish it was bigger.
As for the Bolt, it is basically a Japanese copy of a Sportster, and seems to be just as small. A big part of what attracts me to the 3 bikes in the test is that none of them were Japanese. None of them are copies, they are all original, and they all have a heritage. They are not exactly the same as their half a century old ancestors, but they are remarkably close considering some of the high tech junk out there today.