I'm befriended with the guys at Höfner's in Germany, so I can ask some questions to them if you'd like. The main guy is in hospital now, though.... He wrote the Höfner Violin Bass Book. But this is what I know, think and experienced. I played quite a lot. At the moment I have a German Club and a HCT Club. The German one has different pickups and the Cavern spacing, so not east to do a good comparison. But my cup of tea (pun intended):
Ignition/HI/Icon:
Nice basses for the money. Nice basses if you want a Beatles Bass (or Club) for studio, some songs, a back ip. Some purist like them better than the HCT, because they're totally hollow, like you said. Nice sound, but they look and feel a bit cheap (well they are cheap, haha) and the looks are not totally the same as the German ones. Wrong pickups, cheap looking plastics, strange logoscript on the headstock. My local shop have several and I think they're made in different factories. I saw at least three different headstock logo scripts, different tuners, different strings, different controls. All similar, but slightly different.
A big difference is the neck. The fretboard is almost flat on the body, like a 'normal' bass, so the pickups and bridge are quite low. It makes them easier to play if you're used to other basses. On HCT and German basses the neck is set high in the body. Like Gretsch. Macca had his strap in the gap between body and neck, where it 'hangs over' the body. Pickups and bridge are much higher on the body.
Contemporary/HTC:
I like those. Apart from the controls (you can change them to tea cups easily) they look and feel the same as German ones. If you ad tea cups, they would fool me. I can see it's a HCT because of the different colour sunburst (more black to yellow than brown to yellow) and they're better made than German ones, haha! German ones all have their little 'character' things. Little errors and faults. Hardly noticable, but you can see they're made by humans, the old way. (*)
The HCT's have the center block, but they're still very light. The sound is not that different. It still is a small box, put flats on it and they sound really old fashioned Höfner.
(*) I would advice everyone to buy a HCT cos they're really good and beautiful. But still. A real one. The case, the smell, the look, the wood. Different lacquering. Mojo, magic, whatever you call it. I have two German violin basses and they're really something!
Hope this answers your question a bit.