Here's my honest advice: try both on with the backpack you'll actually use. Walk around the store a bit. Lift your arms. Feel how the fabric moves. If you're going to be carrying a bag, the regular fit is going to stay put, while an oversized tee might ride up or shift.

And think about what you'll be doing. If your trip is mostly beach and hammocks, oversized is the move. If you're planning to explore cities, take photos, and maybe hit a nice dinner, regular fit is the safer choice.

Whichever you pick, you'll be fine. Just remember: fabric weight matters more than fit, and the best tee is the one you'll actually wear. If you're still torn, get one of each—they take up the same space in your bag if you roll them right.