When doing B2B with big corps developers opinion is not of such huge importance, they're not making any calls about closing the deal. Also integration will almost always be a part of the deal, so again devs care less, they'll have someone to come over and help set it up. It's in a big contrast with startups and small teams where it's usually up to devs to choose which payment processor will be used and how, and they'll be the ones expected to integrate it.
Developpers opinion doesn't matter much, but developpment cost and reliability does. If a project takes 6 months vs 3 weeks, it's a completely different game.
Even for big B2B corps, it's the difference between a project you can lead on your own and get credit for it, or something that will go upper in the chain because of all the approvals you need for it.
In a previous life, to get an Adyen contract and dev. environment and then the prod credentials, it took us something like 3 months, and we had a smaller PSP integrated for a different project in the meantime. That meant that for any project we didn't have as much volume, we'd go though faster PSPs instead of reusing the Adyen connection.
My experience is that developer opinions don't matter "today", but today's ICs move up the ladder and matter "tomorrow". Much as how consumer brands work so hard to capture teenagers, because brand loyalty acquired in that period can last for decades.
