The answer considers three perspectives
Let’s Encrypt was being crossed signed by IdenTrust which was the leading CA and still leading Certification Authority (CA) in commercial SSL Certificates.
Therefore technically, Lets Encrypt is as good as any other domain validated (commercial) SSL certificates.
Your customer or web visitor might question your inability or reluctance to invest in a commercial SSL certificate.
Everyone knows Lets Encrypt is free and yes, we people check the SSL Certificate provider.
If your website doesnot have a commercial functionality – go for Lets Encrypt and other Free SSL Certificates such as Cpanel and CloudFlare.
Convenience – Period/ Renewal
Most Free SSL certificates are issued for a period of 30 days or 90 days so you have to renew after 90 days – including Lets Encrypt.
Commercial SSL certificates are issued for a period of 2 year or 1 year and therefore more time before you are forced to renew your SSL certificate.