It depends on the size of the dent!
A small dent in your booster boxes cardboard may shave more than 5% off your eventual sale price to a collectors used to perfection… however to your average person looking to rip booster packs of a set they particularly liked back in the day it’s really not a big deal and they may buy at full price.
However a large dent is a big deal. A large dent could mean that the booster packs inside are damaged. You will not get a good sale price on heavily damaged boxes. It’s pretty much always better to just rip the box open and either rip the packs yourself or sell them individually.
And if you have a dent and a rip in the shrink-wrap, same deal. You’ve lost some of the collectability of the booster box and now have to weigh the value of simply opening it versus selling a damaged box.
Ultimately what you do will be dictated by market conditions at the time… you may find that even damaged booster boxes are valued fully in future. Pokemon is strange like that.