First, tonally, the body shapes really don't impact anything. The Century can have the same electronics as the other body styles, so, for the most part, it is an aesthetic choice. Any body style of a Roscoe with the standard Bart electronics package sounds absolutely NOTHING like a J Bass.
Secondly, there is little similarity between the Century body and a more traditional J Bass body. I think those comments come from the distance between the strap buttons (i.e., the extended top horn), which is similar to a J bass, resulting in very good balance on the strap. If anything, the Century is somewhat similar to the MTD body style to my eye.
Here is a picture of a J body (Alleva Coppolo) next to my Roscoe Century. Given that the J is 21 fret and the Roscoe is 24, you can really see how much closer to the bridge both pickups are on the Roscoe (even compared to the 70's J position of the A-C), resulting, in combination with those warm, fat Barts, that classic burpy, articulate Roscoe tone IMO.
I have played both other body styles, and they are fine, although I personally felt the balance on the 5 string on that smallest body style was a touch neck heavy. Luckily, I found the Century body style my preference aesthetically, so it all became a moot issue for me.