my kiddo's aren't spaced that way but I'm the oldest of 3. Me and my sis are 3 years a part, me and little brother are 8 years apart.
There is a difference-- more of a parental feeling towards my brother. In fact, when I had my son, I was shocked at how much I remembered about my brother when he was a baby. That being said, I still think we are close. He is more likely to call my younger sister about clothes and girl advice, but more likely to call me for advice on money, or my parents, or school/career. Admittedly, my sister is a much better dresser.
The closest brother and sister I know have a 10 year age gap; but whethered a lot of struggles together. She used to go to parent teach conference for her brother, and is still involved heavily in his life.
I guess what I'm trying to say, is that with a gap, the relationship can be different, but I don't think that spacing has much to do with how *close* you are to another. Your new baby will be loved. GL with whatever you decide!