I recently went through this same exercise with my dual pvs14’s.
I bought mine off of the EE for a good deal and even with the cost of the katana housing and conversion i came out a little ahead or equal to selling the pvs-14’s and buying duals outright.
The advantages for me was i didn’t have to mess with selling anything, i didn’t have to worry about the specs on the new duals and only had to wait the lead time to have the 14’s converted to the katanas. (Versus selling and then buying the duals)
It’s going to be different in each case but that’s what worked for me and I’ve been very happy with the outcome.