Originally Posted by
AlohaDaveKennedy
You can't economically do a coversion - transfers and exchanges are not in your favor. Go with whomever has the best price and consider an AMEX SPG to top off the Delta miles, if needed. You may also just use the existing Skymiles for flights. Delta Skypesos are somewhat the Nigerian Dollars of frequent flyer awards - worth a bit less than other program's currency.
The SPG you need to have 20k points to get the 5k bonus, but if you have the Delta Amex you would get 5k bonus at $15k and $25k spend.