The concertinos with the bi-ampable inputs is the first generation of them. The ones with single inputs could be the concertino homes or domus. All 3 generations had different drivers and sound different. I like the 2nd generation best personally(concertino home) but I'm not sure which is most sought after.
Sonus Faber Concertino differences
I've been looking around a some concertinos on the used market and have noticed that there are some with single and others with dual binding posts. I was just wondering about that, and which pair are more sought after. It seems that the model with dual posts are going for more, but it could just be an anomaly.