Originally Posted by UAX_Brasilia

For travel outside Region 1:

You can only upgrade C, D, Y, B, M, H with miles. SWU upgrades C, D, Y, B, E, M, U, H, Q, V, W. Both need NC/NF inventory and both can be confirmed at booking or anytime after.

Originally Posted by mahasamatman

As a 1K, it doesn't make any difference which you use. Though you might consider an SWU easier simply because you can upgrade on a cheaper fare (easier on your wallet).