Netflix is offering 2500 American Airlines miles for new enrollment. Offer expires May 31.
The United Mileage Plus offer is just 2000 miles with signup but another 2000 miles if you charge your membership to a United Visa. Total 4000 miles, and no clear expiration date on the offer.
If you’re already a member, consider cancelling (copy down your queue first!) and signing up someone else in the house with a different credit card. If you’ve already gotten the United bonus, consider cancelling and signing up someone else for the American bonus. Or vice versa.