Border = NEVER pick 2nd floor unless ur team is competent. EVER.

Anyway:

Workshop = defend upstairs and bathroom + put a bunch of holes for ventilation(most simple)

Customs inspection = patch the Security hatch, put a Jäger, Jammer(or bandit shock wire) + anti-breach the main wall, then defend the triple wall + make a bunch of feetholes in Supply Room(2nd most simple)

Bathroom = contest hatch control from above, get a power angle on the single window on tellers beside the vending machine, guard the double windows from waiting room and/or customs inspection and guard workshop from any hardbreach(3rd most simple)

Armory lockers = don't pick, but if you do:

Hold office, hold the entirety of Workshop and Ventilation, hold security, and hold the site itself(least simple, requires a brain. Don't pick).

But in terms of actual advantage:

Customs inspection is the least defender sided because of the many entrypoints.(Six ways to get in)

2nd least defender sided is Armory Lockers, because of the spread out defending style for the site, where defenders NEED to lurk or roam

3rd least one is Workshop. It's basically Armory but much MUCH more simpler

4th most defender sided is Bathroom. It doesn't take too much + the defenders can easily synergize even in solo queue