First of all , It is Xperia not Experia :P
And you should probably get the Xperia Z2
I am not saying that the Xperia Z2 is better but it is because The OnePlus One is only available through an invite system. This means that only people who received an invitation from one of their friends or from OnePlus will be able to buy the device. After buying the device, you will receive a number of invitations that you can send to friends interested in the OnePlus One.
Plus I think accessories and maintenance for the Xperia Z2 will always be much easier to find. so yup Go for the Xperia Z2.