u/throw__away3_

I have a US one and once I obtain my other one (from an EU country) I'd obviously travel with both on hand.

A coworker who travels often to a different country says you should only show them the same passport going there and back and I forgot her reasoning as it didn't really make sense to me. Lets say I travel to the EU from the US should I use that passport when going there and the US one when coming back, or is my coworker right to say I need to just use the US one for the whole trip? I haven't been outside the country in 10 years so I have kinda forgotten how things work.

Since I am a citizen of both countries would it even matter? Like If I use the EU one for coming back to the US why would it matter since people come from the EU for visiting all the time and they are allowed in.