At the time of this writing I believe that with respect to deciding where to purchase a wildcard SSL certificate, the only factors that matter are the first year's cost of an SSL certificate, and the pleasantness of the seller's website (i.e. user experience) for the purchase and setup of the certificate.
I am aware of the following:
Claims about warranties (e.g. $10K, $1.25M) are marketing gimmicks - these warranties protect the users of a given website against the possibility that the CA issues a certificate to a fraudster (e.g. phishing site) and the user loses money as a result (but, ask yourself: is someone spending/losing $10K or more on your fraudulent site? oh wait, you are not a fraudster? no point.)
It is necessary to generate a 2048-bit CSR (Certificate signing request ) private key to activate your SSL certificate. According to modern security standards using CSR codes with private key size less than 2048 bits is not allowed.
Claims of 99+%. 99.3%. or
99.9% browser/device compatibility.
Claims of fast issuance and easy install .
It is nice to have a money-back satisfaction guarantee (15 and 30 days are common).
The following list of wildcard SSL certificate prices and issuing authorities and resellers was created on May 27, 2014:
* Note that Namecheap, DNSimple and sslpoint are resellers, not Certificate Authorities.
Namecheap offers a choice of Comodo/PostiveSSL and Comodo/EssentialSSL (though there is no technical difference between the two, just branding - I asked both Namecheap and Comodo about this - whereas EssentialSSL costs a few dollars more (USD$100)). DNSimple resells Comodo's EssentialSSL, which, again, is technically identical to Comodo's PositiveSSL.
Note that Namecheap and DNSimple provide not only the cheapest wildcard SSL certs, but they also have the least marketing gimmicks of all the sites I reviewed, and I am pretty sure I can say that DNSimple seems to have zero; hence for the convenience of others I am providing direct links to these two resellers: