If I need HTTPS / SSL encryption on my web site, does it matter who I get my certificate from? Are some SSL certificate vendors better than others? If so, why?
If price is your main concern then it probably doesn't matter. However, I think some brands are trusted more than others e.g. Verisign is more well known than Comodo, so your users may be more comfortable if you go with Verisign.
We have seen that Google has different "trust" signals in how it ranks pages. One of these is that the more expensive your technology, the less likely you are to be a fly-by-night spam outfit. Spammers don't spend money on SSLs, and definitely not a nice Verisign SSL.