We have been using Site5 for past one year, mainly for our sites under development or beta stages. While their speed is not the best, it is still not the worst. Definitely we could not find it lightning speed as they have named their best plan. 

One thing we liked about the plan was that you will get a separate cpanel for each of your sites. This will help you a lot if different developers are working on different sites.

Also, one thing we liked about Site5 was that, their ticket based support gets back usually within 24 hours max.

Bluehost is one of the very old providers we have tried. It used to be very good initially and due to some bad experiences with uptime, we had moved to another host. Recently we found that Bluehost has now an India site that will accept payments in INR and hence you don't have to pay any dollar conversion fee.

They have also introduced some new concepts like Dev Cloud and Cloud sites. Cloud Sites boasts of a higher performance than regular shared hosting. Even Reseleller club also sells similar hosting in partnership with bluehost we believe.

I have been using siteground for some time now and I was overall happy with their services, even though there has been some bad time as well. But the good part was they were ready to do things to change the bad to good.