Selfhosted

The main benefits to paying for certs are

• as many said, getting more than 90 days validity for certs that are harder to rotate, or the automation hasn't been done.
• higher rate limits for issuing and renewing certs, you can ask letsencrypt to up limits, but you can still hit them.
• you can get certs for things other than web sites, ie code signing.

The only thing that matters to most people is that they don't get cert errors going to/using a web site, or installing software. Any CA that is in the browsers, OS and various language trust stores is the same to that effect.

The rules for inclusion in the browsers trust stores are strict (many of the Linux distros and language trust stores just use the Mozilla cert set), which is where the trust comes from.

Which CA provider you choose doesn't change your potential attack surface. The question on attack surface seems like it might come from lacking understanding of how certs and signing work.

A cert has 2 parts public cert and private key, CAs sign your sites public cert with their private key, they never have or need your private key. Public certs can be used to verify something was signed by the private key. Public certs can be used to encrypt data such that only the private key can decrypt it.

The point of paid SSL at this stage in the game are the higher tiers of verification. Instead of just verifying that you own the domain, you can verify that you are who you say you are. These are called Extended Validation and Organizational Validation certificates. This has historically been desirable by businesses. It used to be that these higher tier certs would not only give you a lock icon in the address bar of a web browser, but also a little blurb confirming your organization is legit. Not sure if this is still the case though. You will see the extended validation when you check the sites certificate though for sure.

As far as encryption and security, there’s no difference. Also side note, the Comodo brand still technically exists but it was bought by Sectigo like 7 years ago.

Worked as a sysadmin for years dealing with all kinds of certificates. Liek others have said if you can't automate the process a paid certificate buys you 12 months at a time in validity. Also wildcard certificates are more difficult to do automated with let's encrypt. If you want EV certificates (where the cert company actually calls you up and verifies you're the company you claim to be) you also need to go the paid route

In my experience trustworthyness of certs is not an issue with LE. I sometimes check websites certs and of I see they're LE I'm more like "Good for them"