Question [Q] for use on AT&T...T-Mobile S5? Google Play HTC M8? HTC M8 Dev Edition? [/Q]

Hi everyone,

I've owned a Samsung S4 (AT&T branded), a Nexus 5 (GPe), and currently own an LG G2 (AT&T branded) and Moto G (GPe). Admittedly, while the Moto G is an awesome device to test apps and develops them on, I'm looking to gift it to a family member and purchase the best unlocked BOOTLOADER smartphone out there. If the S5 were in the play store, I'd get it right away, but right now I haven't even seen a 32GB version that will run all AT&T LTE bands.

So, here are my options: S5 (T-Mobile off-contract), M8 (Google Play Edition), or M8 (HTC Dev Edition). An unlocked bootloader is absolutely necessary if I'm going to shell out that much money. Also, up for consideration instead of getting any of these phones is a Samsung S4 (Google Play Edition). The only reason I'm looking into the S4 is because I have so many accessories for it, it would be a shame to let them go to waste, especially if it means buying a much cheaper and still powerful phone without having to buy new accessories for the device (case and whatnot). I've heard the S5 is only marginally better than the S4 and in some reviews, aside from the camera quality, the M8 is said to be better. I favor all 3 of these devices because they allow the use of an external SD-card. Ideally, the S5 would be 32GB available in the Play Store, but that apparently isn't going to happen anytime soon and Samsung only has a CDMA (Verizon) developer edition of the S5 available.

So, what does everyone vote on? I'll create a poll, but any reasons you can provide will be much appreciated since I'll hopefully learn more about each device.

Thanks everyone! Looking forward to your replies.