I had both and the decision should come down to how much gain your phono preamp provides. the XA sounds spectacular with the right amount of gain- e.g. 66db minimum, 64db was not enough for me. The XA has better internal wiring and a cleaner, more pure sound and better dynamics but the low .2mV output really demands a quality preamp with enough gain.
The XI is higher output and can shine with as little as 56db gain.
Pick the one your preamp can support.