Debating between these two Eotech sights for my new .50 Beowulf. The xps is an ounce less in weight and just under an inch a half shorter. The location of the buttons I'm indifferent on at the moment, as I haven't used either, but don't think having them on the rear will be a hindrance with the 553. Having the lithium batteries is no biggie as all my flashlights run the same. The 553 comes in FDE to match the rest of the furniture and both qualify for the $50 mail in rebate. Suggestions or experience with these two sights? Will be adding a magnifier down the road.