I come from a brilliant Samsung Galaxy SII, but as I got a hold of the N4 I promised myself I would never buy anything other than a Nexus in the future. There is a simple reason for that; Samsung have been so unfriendly towards developers and this community. I was watching devs working blindfolded to fix some of the most important things for CM10 (butter anyone?), and the device suffered for it. I gave the device to my gf as soon as the N4 came at the post office. Then, Samsung had actually got around to releasing JB, around the start of January if memory serves, and it has brought the device back from the dead. Quality phone, but it'll never beat a Nexus. That's true across the Samsung line, they are so big they don't care about the developers, breaking promise after promise. Samsung won't win me back. Ever.
Before that I had HTC Desire, which was an all right phone. I soon got fed up with Sense though, not going there again.
Sony could win me over in the future, they've been fantastic towards the dev community, going above and beyond(!) what they are required to do. That would still mean paying a lot more money to get (at least) on par with the N4.
That's my reasoning anyway.