If it’s more road-biased I’d be tempted to go with road-biased SPDs:
Hmm I’ve got some A515s on my road bike (I’m not fannying around getting road and mtb versions of shoes so just use mtb spds all round) On a road ride where you clip in at your front door and unclip several hours later back at your front door yep they’re just the ticket but if you’re in and out of them I’d go for 2 sided and for a cross/gravel bikes I’d def go 2 sided.
Dunno those A520s may be better weighted to keep the mechanism top side, so you can clip in easier but the 515s are a faff, flip pedal around with your foot try to clip in, flip clip, flip clip, flip *clunk* there we go. They would be more appealing if the other side was flat compatible for nipping to the shops, but they don’t look to be – negligible weight saving too.
IMO m520s, the 540s are a teensy bit lighter and possibly last a little longer for a fair bit more money (comparatively). I reckon XT and XTR are vastly diminishing returns on your money.