I'd choose Mamoswine.
Meh, that goes with all Ice types not named Articuno or Froslass. Out of the two you've chosen, Mamoswine has a better movepool overall.
INCORRECT. If you have the right weavile set it will pwn practically anything.-_- Its defenses ARE LOW. BUT it's Speed and Attack were made for sweeping. Make him hold Focus Strip/Band(Forgot which one) if your affraid of him OHKOing
Glaceon is seriously better, has MUCH better defenses that Mamoswine so it can survive attacks.
A Lucario's Pulse Bomb OHKOs Glaceon, Same with Mamoswine
Not if what is adamant? If a Lucario is Modest, well BYE BYE TO BOTH. And at least Weavile can counter lucario with Focus Punch.