Firstly, their brains. My kids have two totally different personalities. Cub is more serious, focused, and expressive--probably your typical firstborn. Naomi is free and easy, hilarious, and all kinds of fun--probably your typical second-born. Caleb spoke words and sentences early, but isn't as proficient in motor skills (he still needs help dressing himself). Naomi, on the other hand, speaks primarily in chirps and clicks (ha ha), but her motor skills are much more proficient--she can already partially dress herself and is much more agile (read: coordinated) than Cub. I can attribute those things really only to interest. Cub has no interest in dressing himself. Naomi has only begun having interest in using words. Breastfeeding may have played a part in Cub's memorization ability and such, but I know a lot of breastfed babies that are like Naomi and take a little longer. So, it's hard to tell!
The other issue to look at is health. Cub was a much sicker baby, even though he was breastfed. I remember someone making a snide remark about how her formula-fed baby was never sick, but my breastfed baby was (high-five, witchy Mama!). I attribute that more to the fact that he was early and his lungs weren't as developed as they could be. He had ear infections from an early age and they thought he would have asthma as well (which he does not). But, once he got tubes, he was fine. The kid hasn't been on antibiotics in a year. Naomi, on the other hand, was a healthy baby, despite her tummy issues early on. She was a much stronger baby, I would say. Is that thanks to the formula, or thanks to the fact that she is a girl? Eh, I don't know. I personally think being a girl and being in utero longer worked to her advantage, but who knows! How do we ever know? Asthma runs in our family, so is that why Cub had lung trouble? Could be!
As far as bonding, both of my kids are extremely affectionate and loving and snuggly, so I don't think it affected that at all. And, on a side note, I didn't baby-wear (besides running errands or every now and then around the house), either, and my kids are still super-affectionate and loving. Sometimes I think there's more to personality than we give credit. Everything isn't ALL up to us!
All that to say, I'm pretty inconclusive on feeling that breastfeeding or bottle-feeding affected my kids in a notable way--there are just too many other variables to consider. I still believe breast milk is better since our bodies make it naturally and such. But do I think that babies who are not breastfed suffer in some way? Nope. Do I think that because breast milk is healthy that formula must therefore not be healthy? No. Not in a way that my personal experience has shown me. But, between the two, I prefer breastfeeding, as I've mentioned. But, more than anything, I love my babies. And whatever works best for my babies works for me.
Have a lovely day.