Paralysis, without any hesitation. The #1 rule of strategy is "Never rely on luck" (well, except in some really rare cases).
Explanation: When a Pokemon is confused, it has something like 50% chance of hitting himself. The confusion disappears after 2~7 turns.
When a Pokémon is paralysed, its speed is halved, and it has 50% chance to not do anything. Paralysis never "cures itself" (you have to use a move to remove it).
Because you're absolutely sure paralysis will have at least one negative effect (and a really useful one actually), it's better to chose that.