I'm wondering if it is worthwhile to have go with a second hosting company. I have two sites that are basically the same, but I'm marketing them differently to see what works and what doesnt. My question is, does it hurt me in any way to have to very similar sites on the same IP? I'm using hostgator right now and have around 10 sites. Is there any advantage to putting one of the sites on another hosting site, and therefore a different IP?
No, it does not hurt you to have similar sites on the same IP. The advantage of multiple hosting accounts is redundancy. If one goes down, you still have the rest.
I use different hosting companies for both redundancy and performance. So if a hosting company starts to have network problems or blocks my account for some reason, I can keep going. The performance part is a method I developed to direct traffic from different parts of the world to the closest data center. So US traffic hits my US servers while European traffic goes to my EU server. I'd recommend this kind of setup if you can manage such a complex design and if you have high-traffic sites that need to stay available.
The advantage would be that you would have different IP's for each site which is better for SEO and google ranking. But also, you would have a second bill vs. one.
I use multiple hosting accounts in order to prevent downtime and security problems. I don't know if the seo issue is proven or not.
what's the use of virtual hosting? well there should be no problem with that mate. i tell you, if you're in a shared hosting, it could be that there are hundreds of customers sharing that the same IP.