I agree, at this end of the market it's Shimano, end of discussion. SLX or XT they're both good. There may be minor improvement in the shifting but you start from bloody good anyway. So it's mainly the 40g (ish) weight saving that separates the two. The XT has an aluminium inner sprocket verses SLX steel, so there will be a significant difference in the longevity of this ring. My inner XT ring had noticable wear after 6 months, steel ones go on and on, IME. Up to you to decide which is more important, wear, weight or the logo on the side. You can of course replace rings individually, so no-one would know you had a steel inner on the XT when the time comes to replace it.
I think I've seen XT on Ebay for £120, they're £130 at Merlin Cycles online
SLX – around £90 online