My verdict: the accurate alternative to ZeroBounce.
UseBouncer is known for its accuracy with fewer false positives than competition. The API is solid and the price competitive at $8/1000 verifications. Native integrations are limited but the API compensates. Less known than ZeroBounce but potentially more accurate on certain types of lists.
What I like less: limited native integrations, fewer additional features than ZeroBounce, less comprehensive documentation, smaller community.
My advice: test both (ZeroBounce and UseBouncer) on a sample of your list. Compare accuracy and choose the one that best matches your data.