1) Go to the shop,
2) Hold the three cameras, play with their menu interface,
3) See which one appeal to you most - which user menu, interface, button/scrolls, etc made most sense to you
4) Ask yourself, what is more important to you - of the three only EM5 had some sort of weather sealing, A6000 claimed to be the fastest, and I think both EM10 and A6000 has Wifi (not too sure).
From my personal experience (having owned the EM5 for quite a while now), I find the EM5 could take excellent photos, is easy to use and pretty light. I like my EM5 heaps. I have not handle the EM10 or A6000 before, but a look at the spec and the shape of the A6000, I think it is pretty good a camera too. EM10 on the other hand, shared the same sensor as EM5 (I think), and dumbed down a bit... but with inclusion of Wifi, so I think you could get basically the same IQ as the EM5... minus weather sealing + Wifi, so it is still up to you as to which functions you needed most.