I have tried them all and so far, the best sounding voices I have found came from Synthesia. But it's not cheap. Although, if you just want speech you can use their low-end subscription and audacity to record it. You only get charged credits on downloads and you don't need that. Same for LOVO
But, the voice is not the complete story. I can get fantastic sounding speech from Synthesis, which is not expensive if I spend time making the proper adjustments.
LOVO has one or two decent voices and a lot of voices that they should delete. They are remnants and real crap. But they are supposedly working on being able to record your own voice, with all the emotion, inflections, timing, etc and convert it to a stored voice. That could be a game-changer.
But again, it depends on context. I can create a few sentences in most any product and you would be floored by how great it sounds. But when you start entering your own copy, some of it will still sound like a robotic voice.