I absolutely detested BB12 with a passion.
However, I loved both BB13 and BB14.
In BB13, I loved the house divide, with the Insiders Vs the Outsiders. I also loved some of the tasks, like Turf Wars, which lasted a few days. There were not many twists in BB13, as all the housemates had made the entertainment themselves. Despite a few horrid eviction results. Overall, a pretty good entertaining series.
I loved the theme of BB14, only I wished they'd used it throughout, instead of just the first week. A pretty good bunch of housemates, with different personalities, and ages. On the down side, too many twists, one being overusing the Safe House, which resulted in Slapgate.
Some pretty good Channel 4 style tasks, like Quarantine, Remote Control and Busy Bees tasks.
Despite having a shit winner, the series was very good and I enjoyed it.
I can't really choose between the two, but If I had to, I'd choose BB14, as I watched it all from start to finish, I missed the first month of BB13.