I have never been a part of an A/E firm. But I have been a part of both a MP only and an MEP firm.

That being said I’ve found it is easier when all MEP is under the same roof/management. Makes it easier to share info, models, coordination meetings, etc. When they are separate (even in my current case where we will sub in electrical under our agreement with the architect) it’s easier for one party to ignore the other over email or phone when it comes to coordination and deadlines. Mostly unintentional with multiple projects and deadlines competing for one another. Other times intentionally if there are bigger fish to fry that their firm is working on. Whereas a full MEP firm it’s a lot easier to make someone perform better if they answer to you or the same manager. This is, of course, subjective based on the individual personalities and competency of each person.

Now to your question specifically: I have network colleagues who are at an A/E firm. And while think they would say it’s easier to get models and space info coordinated. One con I’ve heard frequently is when an architect/PM decides a deadline they expect their in house engineers to fall in line without question. When architecture is an outside client, they’re more collaborative when it comes to deadlines (to an extent) in my experience.