American Express Membership Rewards - Convert AMEX card - retain credit history?

If I convert my existing BLUE card to another Amex card (i.e. Clear or Blue Sky, etc.), will I keep my existing credit history on the card or will it appear as if I had "closed" the card.

I know "closing" a card is bad for the credit score since it erases the established credit history on that card, but does "converting" the card have the same effect?

1. "Closing" a credit card does not erase you credit history. It will still report your history until it falls off of your report in 7 years. Closing credit cards hurts your score because it can increase your debt to credit ratio.

2. Converting will not only retain all of your history, with AMEX even if you did cancel the card, anytime in the future when you open a new AMEX product, they will back date it to reflect an account of equivalent age as your first AMEX product.

In summary, converting the card will not hurt your score at all, neither would closing it unless you're carrying debt and you need to preserve your debt to credit ratio.

Does anyone here have Blue Sky, if so, what are your thoughts? Finally getting around to upgrading my 'college' amex to BS or DL Gold. Going the crawl, walk, run upgrade route.