Look up the outcomes in life for adult adoptees. The figures are absolutely horrendous.
Oh for the love of Gawd.
Children who are adopted have worse outcomes across a number of measures because:
Many were harmed by alcohol/illegal substances while in the womb
Many were abused or neglected
Most spent time in the care system which is very destabilizing for children
Their genetic parents are far more likely to be "problematic" people (flakey/addictive/irresponsible/impulsive/tendency to get into terrible relationships and make poor decisions in life/etc.) than the genetic parents of the average member of the population--and that's just talking about personality traits. Large numbers of people who have children removed from them by social services have things like borderline personality disorder, intellectual disabilities, mental illnesses that are difficult to treat/manage and other phenomena. Kids don't get removed unless there are some quite serious issues in the biological family these days.
If adoptive children turn out to have more issues on average (teen pregnancy, dropping out of school, difficulties in educational attainment, higher rates of criminal or otherwise "difficult" behavior), don't fall over in surprise.
And don't start blaming it on some ridiculous "primal wound" crap about how it all stems from the moment they were removed from their biological mother etc. etc. or "it's caused because they were traumatized by being raised by people with different genes/physical features from them!" Bollocks.
Looking at adoptive children tells you nothing about the long-term outcomes for children born through gestational surrogacy.
To learn about the long-term outcomes for children born through gestational surrogacy you need to look at, well, children born through gestational surrogacy.
The data is still a little bit limited because gestational surrogacy is new and rare. As the data trickles in, however, it appears that GS surrogacy kids do fine. They seem to be turning out about the same as the children of any other stable middle-class couple (this being the demographics of most couples who manage to make surrogacy work), and their outcomes are looking nothing like the challenging and trouble outcomes that are sadly common among adopted children.
academic.oup.com/humupd/article/22/2/260/2457841
www.researchgate.net/publication/258823021_Children_of_surrogate_mothers_Psychological_well-being_family_relationships_and_experiences_of_surrogacy
psych.cf.ac.uk/home2/shelton/IJBD_2009.pdf
There is a lack of "gay men" couples in the data--however, given that adopted children of gay men seem to turn out about the same as adopted children of straight couples, I would be surprised if there were any major differences.
I do not deny that there are very some significant ethical concerns about surrogacy--on balance, I am against commercial surrogacy (although I could be persuaded if I heard good enough arguments and data), and think that surrogacy is probably best left to altruistic arrangements where surrogates get expenses-only. But the children born through these arrangements will almost certainly turn out fine.
Some of the comments here have had me thinking "With feminists like these, who needs misogynists?" I am thinking of the comments which seem to think that children will be traumatized by being cared for by anyone except a biological mother, or that not giving a child breastmilk is some sort of abusive act.