How is the Purple Sweet Potato ? Is that Purple Skin, White flesh or Purple Skin, Yellow Flesh ?
I like those types with chestnut flavour.
The Japanese Satsuma Imo is one of the best of those.
There is also the Okinawa Sweet Potato. That has Purple skin and bright purple flesh.

Do you have seeds for either type you recommend?
This one isn't nutty to me but the ube was. It's not as sweet as traditional orange sweet potato. It has a nice texture as though I mashed in butter or cream. It's got more additional flavor, but I don't know how to describe it. It has brown skin with a deep purple interior. I hope the leaves are pretty good. I have grown the Japanese white from the store in a bed at my old house and it took over, so I started using the leaves and they were fantastic.