I used to teach middle school, and at one point, I had 2 sets of identical twins in my class. One of the sets of brothers really did seem just alike. I could not tell them apart physically, and they had similar personalities, earned about the same grades, even had identical handwriting. The other set, however, was quite different. One boy was an outstanding student -- straight A's, always had his hand in the air with a thoughtful answer, carefully prepared homework and tests, but his brother was everything he was not. His clothes looked sloppier,he had different facial expressions, spoke more slowly. They could easily be told apart physically, though they were identical. Also, the slower brother was a "C" student, was more quiet, and had a rather surly attitude sometimes. I would have thought that perhaps he just didn't want to compete with his brother, and thus tried to rebel by being an underachiever, but he truly seemed to struggle academically, though he was trying. I wondered if there may have been a problem with his birth-- like twin A was born first, and twin B had some trouble being born and didn't get oxygen soon enough? Anyway, they should have been genetically identical, and were raised in the same environment, but their I.Q.s as well as personalities were quite different.
Also, when I was in college, there were 2 sets of identical twins in my sorority, and one set were indistinguishable from one another to me (though I didn't know them well). They looked exactly alike, dressed in the same style, had similar personalities. The other set, however, were easily distinguishable. One was about 5 lbs. heavier than the other, they had diferent styles of clothing, one was more outgoing, and their facial expressions were different. Everyone could tell them apart.
Just something to think about. You never know what you will get, even when genetics are controlled!