When I was a kid I didn't even know there were different styles of Aikido. My parents took me to many seminars over the years and I would notice the different styles of training, but it never seemed to be different styles, just different dojos. It all seemed like basically the same Aikido to me.
I think (as someone else said) that the most important thing is the feeling and overall atmosphere of the dojo. It should match what you are looking for. Some styles tend to seem a little more physically demanding, some focus on mental or spiritual strength. This varies between different dojos of the same style too. The main thing is to find a dojo you like.
I really didn't have a choice which style of Aikido to practice, but if you do, just look and you'll feel what's right.