Airline web search sites

[Liz L]

I've heard that it's good to search for airline fares on 3rd party search sites like Kayak, Skyscanner (which then refers over to Hop2, Webjet, etc) JustFly, etc. but then try to purchase the ticket directly from the airline. So far I'm finding the airline fares cost considerably more than the search sites. Has anyone had experience (good and/or bad) with booking through the 3rd party sites? Specifically have you used Hop2, Webjet or JustFly?)
Thanks! Liz