Swapping between shields and deflectors can leave behind bonuses.

[Tetwing]

If you're tinkering with ship builds and go between deflectors and then back to normal shields, if you don't drop the deflectors back to none the AC bonuses still apply even though there's no power or bp spent. Not a huge deal, but it was a monster to track down why my PCs insisted they had a 12 instead of 11.