IMO they're both fine; ignoring the slightly longer walk to the Delta and if price is close, then probably the Marriott for the view from the lounge and the chance of a runway view room. If there's a big price difference, then whichever is cheaper (don't forget to check points rates, it was a decent deal the weekend I was there)

The Marriott base room was one of those that has the odd design choice to have an opaque/frosted window between the bathroom and the sleeping area, which could be awkward if traveling with a non-romantic partner, and annoying for middle-of-the-night restroom trips for traveling partners of any persuasion.

The Delta upgraded me to a suite, can't speak to the regular room layout there.

The only related FT thread I found was this one but it's scant on details: Calgary Airport Marriott In-Terminal vs Delta Hotel Calgary Airport In-Terminal