Well, if you mean host.com, hosting.com and webhost.com, I would say hosting.com. Host.com is shorter, but is too vague, so hosting.com wins. Now, if you mean those keywords + another keyword, that is a different story.
If it were for an actual web hosting company, I'd say Hosting.com would be best. If it were for someone in the hospitality industry, Host would be better. Obviously from a domainers standpoint I think host is the best..It's short and can fit into multiple niches.