A

From a strict SEO perspective, the host won't impact your rankings. That is to say, which host company you're with isn't a ranking factor. But things like uptime, security (if your site gets malware often), speed of site, etc. are all factors that come into play. And Yahoo I don't know enough about the stability and speed of Yahoo hosting to definitively say how good it is in those areas. But I would be willing to bet if we compared Yahoo to someone like WP-Engine which exclusively hosts WordPress sites, that WP-Engine would be infinitely better. Would your rankings improve? Maybe, but it would be more a result of the higher quality hosting, uptime and speed that you get. And yes, I have a recommendation. You should host with us! :)