Do I need a partial crown or a filling? (X-Ray attached)

I went to the dentist for a routine checkup and was told that my Tooth #12 needs a partial crown(onlay). The reason I was given is that since the tooth is too small and the cavity is big enough, the filling would destabilize the entire tooth and a partial crown is the way to go. The X-ray pictures of all teeth are attached, although I don't know which tooth is #12.

Since the partial crown is around $400 (even with insurance) and the filling is around $45, I want to get a second opinion on this. Is an onlay absolutely necessary or should I go to multiple different dentists to try to get a filling? The price itself is not that much of an issue, but i want to make sure that I'm not paying for something that I don't really need.

Thanks for the responses in advance!

https://imgur.com/a/ZTV2A8Y