It is possible they are using the same engine. Could explain why there is nothing on a search about them. They list all their voices. While there are a lot of different voices for languages, I would of expected a lot more of Spanish since that is in the top three in the world of spoken languages. Also , I noticed there is no "A.I." option for SpeechVid, unlike Speechelo.
I am going to do some things in the Mexican market this year, and having a Mexican accent is going to be important, so I am not sure if I will now go with SpeechVid,