So I have seen a few different options and wanted to know what other people use to keep their cards in?

my pilot cards went into ultrapro deck boxes until I won an official X-wing deck box at a tournament.

my upgrades go on their side and in sets of 2 into an ultrapro A4 fake-leather binder thingy, though im considering a box as I need more space efficiency.

Yep thats a similar setup to the one I have now but Im just after something better for the upgrade cards

I keep mine in my foam trays, my extra unique pilot & upgrade cards I keep in tuck boxes.

I have a binder for each faction with baseball card sleeves for the pilot cards, and a separate binder with the same sleeves for the upgrade cards. I put then in sideways and they work pretty well. I keep them organized by type with dividers and alphabetized in each section. you can get two stacks of 5-6 cards in a pocket for the ones you have multiples of, like proton torpedoes.

Good ole Ultra-Pro black leather here.

I have a three-ring binder zippable case (so nothing falls out); using trading card sleeves for the ship cards and business card sleeves for the upgrade cards. I have them organized with dividers into a Rebel section, and Imperial section, and an Upgrades section (plus a section for the rulebooks in page protectors).