Default [Q] Which model is the most open?

I recently became the proud new owner of a SM-900A NC2 note 3. I had a galaxy mega that broke, and my insurance plan replaced it with the note 3. I was actually excited at first. I had been somewhat regretting my choice and wishing I had gone with the note 3 to begin with. But then I discovered that there is no root option for the NC2 update. Nothing. The same was true of my galaxy mega for a long time (SGH-I527). With both of these devices, I noticed that some models were easily rooted/modded, and others (mine) took ages to get a functioning root.

My plan is to be an early adopter of the Note 4 when it's released in September. I don't want to be caught in the same situation where I own one of the models that is very difficult to hack. I want to buy the most open model that can be used on the AT&T network with LTE (Samsung seems keen to release developer editions for verizon, but not with LTE).

Right now, the most open model of the Note 3 seems to be N9005. I'm not going to outright buy a new note 3 that I plan on replacing in 3 months. But when that time comes, are there some rules of thumb that I should know about to choose the most open model? From my limited experience, I've learned that buying through AT&T is a recipe for slavery. But, there are many non-AT&T options.

So, what's the best choice? an International model? A different LTE carrier's model unlocked? Or, is it too early to tell?

Thanks for the help,
Michael