On price, Netlify starts lower at Free/mo against $2.99/mo for SiteGround. Netlify carries the higher rating overall, at 4.7/5, and SiteGround reports the better tracked uptime at 99.99%. SiteGround has been operating longer, since 2004.
If entry price is what decides it, start with Netlify. If rating and reliability matter more than the sticker price, Netlify 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.