I've ridden both and own neither so you can count this as an unbiased opinion, I've rode a few xfs with with 701/760s/865s and one with a 1000 xs, the 865 and 1000 were carbon and I've been on a carbon footrocket with an 865 set up for surf (full length ride plate, which brings it to the length of a JB1, and the tubbies on) and with a 900 set up for flatwater (no tubbies + flush cut ride plate)
I find the Footrocket to be more fun to ride than the xfs, the xfs feels big compared to the skateboard footrocket, the footrocket doesn't ride nose high and as a result is slightly harder to flip but makes up for it with it's rideability.
I recommend the footrocket especially if you're going to be riding in surf as well as flatwater as it's tailored for both.