Hi mamushka
I've done both ( adopt and give birth ) and I'd say that childbirth is a walk in the park compared to the process of adoption . Birth, however bad, only goes on for a day or two . The process of getting a child placed with you will take at least a year , perhaps nearer two.
If you conceive a child you can know about or even control all the background factors and get good antenatal care . Many babies and children who are adopted have been exposed to alcohol or drugs in utero and these can have life long effects .
Many adopted children have a family history of mental health problems , and have been neglected or abused . Again these can have long term effects .
So if your only reason for adopting is because of your fear of childbirth ( which I completely understand as I also had horrible births ) , then you would be better IMO to deal with that issue and then conceive .
There are threads on MN for those who have suffered traumatic births and they will know about resources available to help . You might consider getting a doula, to support you in labour. Or agree an elective section or an early epidural with your medical team . Or learn about alternative pain relief techniques , like hypno birthing.
I'm not trying to put you off adoption , it's a wonderful way for many people to make a family .
But on a strict comparison of " which is easier, a bad labour and birth or an easy adoption? " , it's got to be the first, IME.