What is the best sim card to purchase. We will be traveling in Portugal, Switzerland and France

To my knowledge, you won’t be able to find one that will cover you in all three countries. Switzerland is not EU, so not covered in the free roaming of the EU. The one for Portugal will work in France but not in Switzerland.

I would suggest checking out airalo for purchasing an esim at home before leaving…assuming your phone accepts esim. We have used esim in Spain and Portugal. Bought ahead so can turn on after landing; inexpensive at ~7-12$ per month per ~5 gb. Note that most esim plans are just data plans but we have found that the vast majority of airbnbs etc use WhatsApp…so voice video and texting works fine so connecting is not an issue…