Namely the price, the support and the reliability. My experience with Hotsgator thus far has been nothing but positive. In the last month I have gotten only one warning from Easy Monitor about my sites being down, and this was for a period of only seven minutes. My sites are always quick to load and on the one occasion I've needed to contact tech support the response was quick, courteous and helpful.
What I find especially impressive is that Hostgator does not delete the negative reviews posted in the forum. Some of them are rather harsh, and the fact they let the reviews stand as posted tells me a lot about the company.
I look forward to being a Hostgator reseller for a long time.