Frame and fork looks a better combo on the boardman, but if I got one I’d have to junk the entire drivetrain as I can’t stand SRAM stuff! Totally personal I know, but I hate the way it functions, and that 2 ring FSA chainset with a 15T gap between the rings (which are only 3 bolt, so good luck trying to find replacements!) just looks horrid…
For those reasons I’d buy the Cube myself, maybe a bit more conventional (if a fat tubed ally frame can be described as such) but a full 30spd SLX/XT setup would swing it for me I’m afraid.
You may have no preference whatsoever on the gearing though, swing a leg over both, see what suits. Had a quick look at that Boardman in my local Halfords the other day, and it does look like it should be a tasty ride (except for all the nasty SRAM!) for the money…