doubt there are boots specifically made for defenders/strikers but usually people go with which ones are more comfortable, others because their favorite players wear, them or other reasons.
i play and have played all positions on the pitch, and whenever i was a defender, i usually wore boots that nike define as accuracy boots, such as the total 90s, because they are more comfortable and have extra padding, so id say those are good for defenders, because they tend to slide tackle often and
right now im a striker, i always play with my nike steams ii or my tunits f50.7 because i find them quite fierce actually
you are probably going to take me as a fool, but whenever i play with tunits and the steams ii, they kind of give me that extra confidence/motivation, i would say they are good for strikers, because they dont have a lot of padding thus making a strike be filled with power and making hard for the keeper to cope with, but that depends on the players ability and strength of his or her kick, but for me, the tunits and steams have worked well for me, because when i kick the ball, it seems like a bullet because there is less padding in them and more power put into the hit.
hope this helped, sorry for the long post.