FSX Aircraft: Re-Install or Copy & Paste?

I've waited to make the switch to P3D long enough and plan to install it next week.  When moving FSX aircraft to P3D, is it easier to re-install (using the Migration Tool if needed) or just copy and paste the necessary files from FSX?  I'm thinking that if I copy and paste, I need to do the same with gauge, sound and effects files and will get a lot of old files that aren't really needed.  But, a re-install will require finding all the original downloads and updates.  What is the best way to go?  Thanks!