On price, HostGator starts lower at $2.75/mo against $2.95/mo for Bluehost. Bluehost carries the higher rating overall, at 4.5/5, and Bluehost reports the better tracked uptime at 99.98%. Bluehost has been operating longer, since 1996.
If entry price is what decides it, start with HostGator. If rating and reliability matter more than the sticker price, Bluehost has the edge. Either way, read the full profile before you buy — the trade-offs section on each page covers what the summary numbers leave out.