Cheap Ubiquiti Nanostation M2/M5 would be my first thought - they're external rated, powered by PoE and can link over several Km with a clear LoS (not with your average tablet/phone, but another Nanostation for example), but check the coverage angle as they are directional. The Bullet however isn't directional when equipped with an omni (popular in ship to shore setup's on boats/yachts), they work well enough if you want/need to have (potentially) 360 degree coverage, but again it depends on the mounting point and what gets in the way, nothing wrong with an external AP either. I quite like the Unifi kit, that said TP Link and even Mikrotik can be competitive on price, I have never got on that well with Mikrotik AP's, but it's personal preference and Ubiquiti tends to cause me relatively few issues, for example I put a used bullet+omni on the rear wall of my parents property 5?+ years ago, it's been faultless and is pretty unobtrusive, it's roughly 3/4 of an acre, but it's even good in the neighbours gardens that back onto it, I honestly can't recall ever having an issue with it, that's probably about as good an endorsement as I can give on any networking equipment i've ever owned/installed in the last 3 decades.