To boldly go...where at least one hapless crew has already gone.
Many TOS stories involve the Enterprise
winning out over the bad guys because they are forewarned about what they can expect. In "Balance of Terror," the Enterprise
might have been blasted to atoms if they'd been among those outposts attacked first. The cloaking device and super-gun seemed very advantageous to me.
The Romulans had an excellent chance—they just pushed it too far.