To me the Sphere wheels look easily crushed and the thin outer layer more prone to tearing off. The Sphere wheel also looks to have more pitch which may make it more prone to catching on baggage sorting equipment. The wheels are going to be the most likely failure point of either bag, but I subjectively think the Travelpro looks more robust myself. The non-spinner members of the Marquis line have the same ball-bearing wheel as the Crew line... they're decent by themselves, but they can also be replaced with much smoother rolling in-line skate wheels.