Best consumer focused option
Flystein employs a team of travel experts that'll use their in depth knowledge of airline revenue management practices like fuel dumping and loopholes to help find you the lowest price possible. Always choose their "Beat my price now" option, otherwise you're likely leaving money on the table.
Great for personal but also business travel
While Flightfox is similar to Flystein, they also have a big focus on the more complex needs of business travelers. For personal travel, there's no need to select a special "beat my price" option as that's the standard way they take trip requests which is nice.