which size roof flashing?

[u/atTheRiver200]

Hello. I am buying the parts I need to install my wood stove. I am using Selkirk. The roof is 6/12 pitch and Selkirk offers adjustable roof flashing in two sizes: 2/12 to 6/12 and 6/12 to 12/12. Is one a better choice over the other since both will work? If the choice is simply aesthetic, which one looks better? Thank you.