Which tier? Well they'd both only be viable in NU...
In any case, Armaldo for Rapid Spinning in NU. NU doesn't have a lot of Rapid Spinners, but that's NU for you. Most of them are weak to Stealth Rock themselves, though Wartortle holding Eviolite is a common Rapid Spinner. Armaldo also has the rather unfortunate abysmal speed, meaning it's likely to get KO'd before it can even use Rapid Spin.
Cradily for Storm Drain and immunity to Leech Seed. An okay typing, many of its weaknesses are negated, though it doesn't have too many useful resistances. You can also give it Rest/ Sleep Talk set, along with Curse and one sole attacking move, making it into a poor man's Snorlax (kind of).
If you already have a Rapid Spinner, go with Cradily. It can make a good addition to your NU team and a nice stall, with high defence and special defence.
If you don't have a Rapid Spinner... you don't have a lot of choice in NU, the other viable ones being Torkoal or Wartortle. If this is RU, use Cryogonal instead. At least it can muster itself as a specially defensive wall that has a decent speed.