I will agree that dating as a couple is a whole lot more difficult, and opens you up to a lot more problems aside from the usual issues people deal with in polyamory. Here are some questions I would ask yourself before deciding to find a third party for your relationship:
What happens if you find someone who wants to be with you both, but loves one of you more than the other?
What if they are sexually attracted to one of you more than the other?
What if they get close to you at different rates?
What happens if one of you has an argument with the new person, how will you handle it, will there be taking of sides or can the other of you be impartial?
What if you both fall in love with someone, but find later that one of you is not compatible with this person, will the relationship be allowed to continue with the other person?
Do you want a relationship in which you are all equal, or would you insist on your partnership being above either of your relationships with the new person?
If you do expect that, what happens if one of you ends up developing a closer relationship with the new person than what you have now?
The thing to realize is you can't control how much someone will fall in love with another person, at what rate and what time frame it will happen, what the sexual connection will be, and so on. If you are expecting someone who will love both of you just as much, and be sexually attracted to both of you the same amount, be prepared for a lot of disappointment. Also, realize that you each will be forming separate relationships with this person, and the same as you may want alone time with eachother, you and the new person will also likely need some alone time away from the triad as a while. In addition, unless they are going to be allowed to have other outside partners, and sometimes even if they are, you have to either be willing to make it an equal relationship, or invite resentment and non-fulfillment on the part of the third. I'm not trying to say a triad can't work, I've been involved in a few and they can. I just think its good to prepare for the extra difficulties, figure out if you are suited to having a triad, and figure out what you are comfortable with before problems come up.