I will caveat the above with this observation:

It is true that if you are already a Diamond member in IHG ONE Rewards and you purchase Ambassador status for $200 or 40,000 points, your Diamond status is likely to roll over.

However, I have seen no reports that someone who is currently IHG One Rewards Platinum status who purchases Ambassador status will also thereby ELEVATE their IHG One Rewards Status from Platinum to Diamond.

This could be the case but I would not rely on it as historically, purchasing Ambassador status effectively renewed your current IHG status for another year.

Caveat Emptor!

Great question concerning the above program to drop.

It's great that Hilton does not charge resort or destination fee on award stays but their change with respect to their breakfast credit for US stays has been negative, if not entirely understandable.

IHG on the other hand has gone exactly in the opposite direction whereby current Diamond holders get a decent breakfast -- and at most who have reported, that includes taxes and tip!

Whereas you can always get the Aspire card again (without a SUB) bonus if you drop the card or downgrade to the no annual fee card should you wish to re-establish your Hilton bona fides, you will not be able to do so with IHG if you have Diamond status and drop the program or drop down in the program.

Of course, this will come down to your travel patterns and a more thorough personal review is probably required to conclude what is best for you.