The Dominion were scarier than The Borg!

It could be argued either way. The Federation probably had less of a chance against the Borg (at least if they came in force). The was a bit more equity against the Dominion, but only because the Prophets eventually embargoed Dominion vessels from crossing.

However, just on their own, I can easily see the argument that the Dominion, or at least the Founders, were scarier than the Borg. The Borg are direct and completely unsubtle. The Founders can look like anyone. Paranoia against allies and friends can easily overwhelm a culture given that sort of enemy.

Of course, the Borg winning would lead to a zombie like existence that would be quite horrifying to many.

So, yeah, I've just argued myself into a circle. But, as I said, it can be argued either way.

I'd rather go to war with Dominion and die, than be assimilated into a collective. I think The Borg are much scarier.

Picard was always able to defeat the Borg. They airways had some glaring bugs in their software ("Sleep")