Island Packet gets my vote
I spent the last couple years struggling with the same question. I took Sabre out of the equation early on because it's geared a little more towards racing than cruising. For example, most heavy duty cruisers have a stay sail but the Sabres are ordinary sloop rigged vessels. If you look at all three boats, you'll see that the Calibers and IPs are clearly designed more for cruising. The Sabre's keel is a fin type whereas the IP is a full keel and the Caliber close to that. And so on.I've gone to the Annapolis boat show for three consecutive years each time trying to find what I thought to be the best boat. Of course, "best" varies depending on what you want. You don't buy a Ferrari expecting to move a piano anymore than you buy a cargo van to enter a road race. I thought very highly of the Caliber and it came out tops in my last after leaving Annapolis last year. Further study of it made me put it down a notch under IP. That said, it's still a good boat. I scrutinized it again last week in Annapolis. I still like it but it's missing a level of finish or quality that the IP has. For example, instead of molded in diamond pattern non-skid, the finish on walking surfaces is like a sprayed on random finish that is shiny. The cabin sole is also a shiny, high gloss surface that makes me question how slippery it could become or whether it could would show wear and tear quicker than a duller finish. The portholes are held up by a somewhat flimsy ball type chain (like the kind you may find on a key ring) whereas IP uses a more robust steel hook and eye. The finish out in the IP is just plain better. I also like the full keel even though it may not be as maneuverable. It protects the rudder and prop better which could be important if you crunched into a reef. IP also makes more boats and is a larger manufacturer with a reputation for excellent customer service. That said, each of these are excellent boats. You can't go wrong with a Caliber if that's one you'd like. In many respects, I think the Caliber is something of a copy cat of the IP. There are some amazing similarities. And Caliber doubtlessly offers a few things IP doesn't such as an ever easier access to the fuel filters. You'll have to judge for yourself but at least take comfort in knowing you can't make a wrong decision. I wound up buying an IP 350 but that's just me. Doesn't mean I'm right or that I know enough to make the best decision. Good luck.