Just scrolling through the list of Pokemon allowed in the Tundra Tourney, you can see there's a majority of physical attackers. Therefore, Foul Play will likely be more useful. Smogon's "Notable Pokemon at a glance" includes 31 Pokemon, 16 of which are usually Physical attackers (Not counting ones like Dragapult or Dragonite, which can go either way). Foul Play completely screws set-up sweepers and Moxie Pokemon, such as Gyarados, DD Salamence/Tyranitar, SD Lucario/Rapidash, and Hone Claws Aerodactyl.
Spritomb can, however, run into some problems with special attackers when running Foul Play. Night Shade is nice for reliable, fixed damage, but Foul Play is probably still more useful. Not to mention it's super-effective against a lot of notable special attackers anyway, such as Spectrier, Dragapult, Indeedee, and Espeon.
Smogon Tundra Tourney
List of Tundra Tourney Pokemon