I think you should buy Xiomi Redmi 1S as it is worth buying in terms of the specifications it gives compared to XOLO One. When we compare the specifications, it has more battery backup, high screen size, higher processor speed and camera quality and its pixel density. XOLO One is some what cheaper than Xiomi Redmi 1S.
As far as OS is concerned, you should first make sure, whether you will have much difference in using Android One, Android 5.0 Lollipop or other version of the same OS type. You will just have minor feeling of new or upgradable OS but I think you should look for the overall configuration and performance, you are going to have when you choose Xiomi Redmi 1S.