Continuing the comparison to HG, the two biggest ones I see are no roof top racks needed, and no more bent down tubes from a blown launch or landing! AWD cars work, instead of a pickup or 'burban, seriously, with the price of gas these days (and the big miles being done in XC in both sports) that could be a factor.
The big drawback to both sports is the lack of ability to solo fly. By that I mean, at least here in Idaho back when I was HG'ing, it was a "call everyone up and let's see who we can snag as a driver". Those rigs don't drive themselves back down the mountain, or come pick you up when you land 100 miles away. THIS HAS BEEN RESPONSIBLE FOR DIVORCES! Guess how I know? I love the ability I now enjoy with powered flight of being autonomous, these bad ass's doing the vol bivouac thing don't count, they are on a whole different level, freaks actually, all single for sure, and young guys also

All meant as a compliment! But the biggest freedom I have experienced as a 6 year hg pilot, and 8 year ultralight pilot, and now fixed real wing pilot (ha) has been having my foldup mt bike in a plane that thrives on mo gas, and a 8 hr plus duration. The challenge of any activity can be ratcheted up to any notch one desires, by pushing the limits, and the non powered pilot that doesn't think so hasn't top landed (powered) a new site at 10 K in the middle of nowhere by themselves, a bit different then taking off pavement and staying in the pattern, or for that matter going xc in a HG while in constant radio contact with the sucker, oops I mean driver. When I morphed out of hang gliding and into ultralights, it was because I quickly realized the huge advantage of not having to suck up to drivers constantly, it got to be a huge PITA, and the longer distances involved nowadays (15 or 20 miles was a big deal when I was doing it) means getting home at midnight, and pissed off wife's and girlfriends, or both.

I've heard HG pilot's rhapsodize about the "real" flying they are doing, that is a sure way to set me off, it's all real flying, we just can do it whenever we want, don't need 4x4's to get airborne, though we do have to worry about burning alive and they don't, that seems a small price to pay for the liberty of not needing a driver. Kidding there, I think.