Personally, I would opt for the Support variant.
Having Snarl support is pretty essential on a Doubles team, since switching is so uncommon and the lowering of offensive stats beefs up seemingly frail Pokemon. Anything that is held back by its Special Defense will appreciate Snarl support, for sure.
While the Offensive set isn't bad by any means, I simply think Zarude works very well as a support Pokemon. Out of the options you provided, I would go for Seed Bomb for accuracy and Jolly so you don't have to cut into your bulk. While the Special Defense drop will be patched by Snarl, I would still not take that risk. Snarl isn't meant to do a lot of damage, there's really no point in using a nature for mixed attackers.
If you want to know what I'd choose for the Offensive set, I'd do a Scarf with Power Whip, Lash Out (for Intimidate), and Rock Slide.
Hope this helps! :)