W
Why would you buy a first gen WP8 phone? Seems rather pointless at this stage. Yes it will get the W10 update but it won't get all the features (well nothing under an 830 will get all the features) but you'll come out better with a newer phone than the 720. Unless your requirements are not that high.
Also, there have been a few issues with these devices. The camera is supposed to be good and the phone in general is supposed to be good.
Other than price I wouldn't touch a first gen phone other than the 1520. But that's just me.