Your choice will have to depend on what you feel comfortable with. Anyone else's opinions will be subjective and solely based on their negative or positive experiences of either OS.
My views are (remember what I said above :wink
, Android had so much potential and yet fell into the comfy armchair and stagnated somewhat. Each release is usually just bug fixes. The material design in Lollipop was refreshing, and the change from Dalvik to ART, but underneath, it was the same old.
The LG is a good device, but like many devices, even on W10M, they are only as good as the software on them. I like LG, purely because they aren't damn Samsungs! Saying that, this new LG modular design seems to be 'odd' with plugging different things in, where many devices have it all in (to an extent).
The 1520, for me, is the daddy of pretty much all previous generation flagships. I like the size, I like the form, I Like the aesthics of it, and W8.1 made it a flying beast of a phone! Windows 10 M, especially the Redstone Previews have unleashed the beast again. There is little to fault this device on. The device is probably one of the best phones in the past couple of years. But, it is let down, for some, by the perceived lack of apps. It is getting there, but it will be a long haul.
So, I'd keep the 1520, ditch the 720, and save up for the LG, although with anything Android, you need to be sure that you will get OS support beyond a year!!!
Told you it was going to be subjective. I have developed / cooked roms for android, but Win10 is for me.
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