I have been wondering about this issue a lot recently.
Going on my own experience, I have given birth twice, and they were very different experiences.
The first was a horrendous 13-hour stretch with lots of pain relief, followed by a real struggle to get breastfeeding going.
The second was fantastic. No pain relief, because it all happened so quickly (not because I didn't want any!), all over in 2 hours (much to the midwife's surprise!), followed by an easy start to breastfeeding. I did have some difficulties later on with bf, but that was several weeks later, unrelated to the birth.
The thing is, I'm not sure whether the 1st time it was more to do with my own inexperience, general exhaustion and the lack of support that affected bf, or whether pain relief also played a part.