Here's an objective view, although I personally will not redeem Marriott points for stays unless the value is 1.5 cents or greater.
Here is a link where you can check out the conversion rates between points and miles.
You also have the option to purchase airline tickets directly with your Marriott Rewards points at this link:
Hope that helps! Let us know if you have any more questions.
Thanks for sharing, but 1.3 million points for 2 one-way first class tickets to LHR?? I booked the same with 140,000 Delta miles. I've looked at Marriott's airfare deals and have never found anything reasonable. I think MR points have the most value at Marriott properties. Especially the stay 4 nights on points and the 5th night is free.
Maybe the United miles deal has some value -- I'll take a closer look.
Thanks for the help!
I agree with the 5th night free creating the most value. That is why I always try to make vacations last either 5 or 10 nights exactly. This summer, I'll be doing my first 7 night travel package which also seems like a good deal (6 nights worth of points for the hotel - still 1 night free, and a 1:1 point transfer to the airline).
I think a good rule of thumb is points/miles are usually most valuable when earned and redeemed within the program they originate. Transferring/choosing to earn in another program typically comes with some sort of dilution.
In the OP's case I'd keep on earning (and start spending some) Marriott points.
I've done math on many reward programs I'm a member of. Bottom line is that normally the best return rate is using the points at the company of the program owner. So use your MR points at Marriott, SPG points at Starwood, MilagePlus miles at United, etc.
Earning miles directly through Marriott has a terrible rate. However, since you can freely switch, look out for the promotions (I know there are a lot Aeroplan promotions with Marriott/Delta). Also, Marriott allows for a larger amount of MR points to be exchanged towards airline miles, which makes for a lot better deal.