How to position the tip of the tongue when pronouncing /s/ & /z/?

This website says, when making /s/ & /z/ sound, the tip of the tongue should be close to the upper backside of the top front teeth.

But this video says, when making /s/ & /z/ sound, the tip of the tongue is down, slightly touching behind the bottom front teeth.

So who is right?

I personally think that the 2nd is right because I feel more comfortable when letting the tip of my tongue behind the bottom front teeth & I feel uncomfortable when letting the tip of my tongue behind the top front teeth.

It could be there are many way to make the sound. Maybe the tip of the tongue in this case does not play a very critical role in making /s/ & /z/

/s/ and /z/ are alveolar fricatives. The tip of the tongue is positioned just off the alveolar ridge, just behind your top teeth. The place of articulation, where the tongue tip is positioned, is the same as for the stop consonant /t/.

English does not have a fricative where the tongue tip is behind the bottom teeth, but some other languages do. I think I have found some that do - it is a little bit tricky because the tip of the tongue is not very significant for these sounds, and so the tongue tip might not always be positioned in the same way. You can listen to recordings of these at Wikipedia: