Before you make any more decisions you need to answer that question.
A rational decision is based on testing and data and an understanding of the mechanics underneath the system you're working on. The more you know, the better you decide.
An irrational decision is based on gut instincts, conviction and faith.
No one is rational all the time. In fact, somewhere along the way we made 'irrational' into a bad word, but it shouldn't be.
There are card counters in Las Vegas who are rational about blackjack. And they make a decent living. The more they play, the better they will do. In the same casino, there are craps players who blow on the dice, wiggle their hips and wear lucky shoes. Inevitably, if they play long enough, they will be broke.
If you're running Adwords on Google, I hope you're making rational decisions based on clickthrough and conversion.
On the other hand, were you rational when you fell in love? Did you do the math? Medical analysis?
What about the last time you fell for an April Fools joke?
The very nature of faith is that you don't (and shouldn't be) rational about it. In fact, you're entitled to be aghast when anyone confronts you with proof. Proof and rationality aren't the point.
Same with fine art. If your taste in paintings or music or wine is based on some sort of rational analysis or Zagats-type survey, I feel quite badly for you. Deeper and more detailed information is not better information when you're making irrational decisions. If you need to hate on Copernicus in order to have more faith, something is seriously wrong.
When Chris Blackwell introduced reggae to the rest of the world (Bob Marley!), it was irrational. That moment in time was the best time to be working with Bonnie Raitt or Jackson Browne, not some unknown spleef-smoking guys from a tiny island in the Caribbean. No amount of rational analysis would have led an investor to back Chris.
Irrational passion is the key change agent of our economy. Faith and beauty and a desire to change things can't be easily quantified, and we can't live without them.
Steve Jobs is irrational about product design. As a result, focus groups make no sense. Who cares what other people think? He has faith in his gut. Your website: is it rationally designed? Should it be? What about the process you use to create new products or ads? Or the way you pick the focus of your startup? There's room for both rational and irrational decision making, and I think we do best when we choose our path in advance instead of pretending to do one when we're actually doing the other. The worst thing we can do is force one when we actually need the other.