Tested every option during 10 days in Paris. Here's what worked:

Best value: Orange Prepaid SIM €20 for 20GB, works in Métro stations unlike most tourist SIM cards. Buy at Orange stores near République or Châtelet, not CDG airport kiosks which charge double.

Pocket wifi: Skip it. Paris has free wifi everywhere now and pocket wifi devices die after 6 hours.

International roaming: Check your home plan first — Some US carriers include EU roaming now.

Free wifi reality: every café around Saint-Germain, McDonald's on Champs-Élysées, Métro stations on Lines 1 and 14, major attractions. Password usually 'password' or ask staff.

Data needs: Google Maps offline mode for Métro navigation, WhatsApp, occasional Instagram from Eiffel Tower. Unless you're streaming video, 20GB lasts easily for week in Paris.