A certificate is a certificate*, and Comodo has been pretty well established as a bad actor in this field due to their nonstop FUD against Let’s Encrypt (to the extent of using their own web browser to mark sites using Let’s Encrypt certs as “not secure”, or attempting to trademark Let’s Encrypt themselves). The certificate doesn’t dictate the kind or strength of the encryption used. Bottom line, use the cert from Let’s Encrypt; there’s simply no need for anything else.
*Well, mostly. Certs can be DV (domain validation), OV (organization validation), or EV (extended validation), differing in what they validate (and, naturally, the cost). A DV cert validates that it does in fact belong to the domain it names. An OV cert validates that it belongs to the organization it names (though nothing shows you this in a browser unless you drill down to the certificate details). An EV cert does the same thing as an OV cert, only more so–and historically has given the “green bar” in the browser, though that’s going away shortly. No variety of cert validates that its owner is a “good guy,” and there’s absolutely no difference in encryption levels among them.