When it comes to space saving, a straight ladder is your best climbing option as staircases take up a lot of floor space. You can opt for a staircase if the triple loft bed is long and narrow so long as it doesn’t protrude from the bed. If a staircase provides extra storage, take note of the storage space saved.
As for safety, the safest climbing option is a staircase as it doesn’t just offer the largest surface for stepping on, but it also comes with a built-in handrail. If you’re concerned about safety, you can also opt for an angled ladder instead of a straight ladder as it’s less treacherous and the angle makes going in and out of the top bunk easier.