Hostgator Pro's:
1. Hostgator uses Cpanel - which is more common industry wide, meaning less comparability issues, more plugins/ect work. Dreamhost on the other hand, uses their own proprietary control pannel.
2. Hostgator has phone/email support, they are actually fairly good and fix issues fairly quickly.
3. Hostgator overall has better uptime, servers,ect. Dreamhost has a history of a lot of problems, and overloading servers. If you have downtime, it can last for hours or 1+ day. If everything is good and you are on a good server, then you don't notice anything.
4. Reseller hosting - will allow you to have a unique account for each domain you setup.
Hostgator Con's
1. Really none. Other than it will cost slightly more than your Dreamhost account.
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Changing hosting providers is never fun, depending on how many websites you have and need to transfer over, and any issues, I would try to find a hosting provider that if you make a switch you will stay with for a long time. If you have only a couple websites and have not prepaid, it may make sense to move to a company like hostgator, since overall uptime and service are a lot better than Dreamhost.
If you are not having many issues and don't need to be up 24/7 (i.e. not paying for traffic ect and some minor downtime won't hurt you monetarily). Then I would probably just wait until you grow to the point where you need your own VPS or dedicated server and then look for the most reputable company. Dreamhost just is a budget host, always has been always will be, that besides price doesn't offer a great value to hosting with them.
PS: This is all assuming you are just using a hosting provider to host your own sites. If you are seriously consider hosting client sites or offering reseller hosting, then you certainly want to find the best provider with rock solid servers. And support.
