Keep them both shiny. You'll have read through other threads on here that the soles crumble after a given period. That period may come when you really need a pair of shiny boots, so you'll have the other pair that you can just slip on.
Of course, given that you're issued with the boots at the same time, you'll slip on the second pair and find that their soles have also crumbled.
Why would I assume that? Whichever one is issued is the correct one. Technically, I could parade in the jacket I was issued in 1981 as only one of the two then issued had to be exchanged for the CS95 Field Jacket.