Who offers best WP hosting?

I'm trying to find out which hosting company would be best to deal with. I'm currently with blue host, and I was also looking at WP engine and want to know what people's opinions were of WP engine service?

My plan is to have a multisite installation and build WordPress sites for local businesses, potentially having more than 50 sites. So I'm looking for a hosting company with good security, etc.

Take care
Eric