if you've never had a japanese sweet potato (satsuma imo) i highly recommend trying them. different from the orange sweet potatoes we are used to here, drier and starchier but delicious. i get them at the asian grocery stores. they are best baked whole in skin for a long time, insanely sweet ! i think these are the best kind
there's also purple fleshed sweet potatoes which are good and high in the antioxidant anthocyanin