On price, Bluehost starts lower at $2.95/mo against $2.99/mo for SiteGround. SiteGround carries the higher rating overall, at 4.7/5, and SiteGround reports the better tracked uptime at 99.99%. Bluehost has been operating longer, since 1996.
If entry price is what decides it, start with Bluehost. If rating and reliability matter more than the sticker price, SiteGround 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.