[Q] Which GSM version is most "hacker friendly"? What are the tradeoffs? topic

I'm frustrated with the locked bootloader and lack of developer interest and no Ant+ on the latest update so I am going to buy a phone that does not annoy me. Note 3 is my leading choice but I am also considering the Xperia Z Ultra Google Play Edition.

Right now, I've got more money than time. I have tons of good paying work backed up and I would rather pay for what I want than try to stay one step ahead of some carrier's control issues / bloatware.

I'm on AT&T with a grandfathered unlimited data plan. Don't really need LTE but will take it if it makes no difference. I do want at least HSPDA.

I'm willing to shell out the full cash price for an unlocked phone with an unlocked bootloader. What I really want is a phone that will get timely updates from the manufacturer and won't try to shove a locked bootloader down my throat later. It would also be fantastic if I could get a USA warranty in the deal but I can live without that.

So is there a significant "hacker friendliness" difference between the various models? If I give up AT&T LTE frequencies for the international version, what am I getting in return (besides the obvious international frequencies)?

Thanks for your time,
David