I got the shovel + axe attachment. Here's a photo from a recent trip.
It is kind of pricey, but it's certainly heavy duty. And it's convenient to have those tools immediately available, yet out of the way. It's kind of ritual when I transition from highway driving to the trail: that's when I move the shovel and axe to the roof rack.
I had some second thoughts about the weight of the hi-lift outboard attachment, as others have mentioned. I usually strap the hi-lift (and other recovery stuff I hope I won't use) on the rack for longer trips. It's still up high, but at least centered. It probably makes a 0.001 percent difference in COG