Using different passports for Entry/Exit when passport-officials from both countries sit at the same desk

I have dual citizenship - let us say passport P1 and passport P2. I am living in country C1 on passport P1, but my tourist visa for P1 is about to run out. My plan is to travel to neighboring country C2 for a few days, and then return to C1 to stay on passport P2. In order to accomplish this, I need to do one of the following :

Option-1

On the day I leave C1 :

• Exit C1 on passport P1
• Enter C2 on passport P2

On the day I re-enter C1 :

• Exit C2 on passport P2
• Enter C1 on passport P2

Option-2

On the day I leave C1 :

• Exit C1 on passport P1
• Enter C2 on passport P1

On the day I re-enter C1 :

• Exit C2 on passport P1
• Enter C1 on passport P2

Questions

Either way, on one of the days I have to exit one country on a different passport than I use to enter the other country. I figure that this is in principle possible, but what I am worried about is this - I have heard that at the border of the two countries, the passport-officials for each country both sit at the same desk together. Does this mean that they may insist that I enter one country on the same passport that I use to exit the other? Does anyone have experience with this exact situation? Should I avoid this situation by travelling by plane to a country which does not share a physical border with the one I am in?

I figure that perhaps Option-1 is slightly better, because in that case, the day of the passport-switch does not involve me entering a country for which one of my visas is already used-up.

Thank you for your help!

I am curious about this question in general, but if it is a case-by-case sort of thing, these are the actual details in terms of the passports/countries :

• C1: Argentina

• C2: Uruguay

• P1: US Passport

• P2: Italian Passport