Indeed you are in a similar situation!
I'm not sure about the affect on your credit score, but I'd think there's plenty of advice to be found on that.
I'm going to wait until my 1st year of Amex Plat is up in July then make a decision. If I still want an Amex Plat I will definitely close it and reopen one via the corporate advantage program. However, since I may be flying mostly United I will consider switching to Chase Sapphire Resever (since they are a transfer partner, and Amex isn't with United).
That said, getting a $150 discount on the Amex Plat may be too tempting. I'll always use the airline credit, uber credits, and a few other perks.