Short answer: start with source-image support, duration and resolution choices, output reliability, queue behavior, and whether the result stays connected to the image and prompt that created it.
Start with the source
Image-to-video tools are most useful when the source image, video prompt, and completed result remain grouped. That lets you make a new motion pass without hunting for an old download or guessing the original prompt.
Look past the advertised duration
A longer clip is not automatically more useful. Check whether the duration fits your edit, whether the available resolution works for the destination, and whether the tool clearly shows the settings before you send the generation.
Expect a queue, but expect clear status too
Video generation can take longer than image generation. A useful product distinguishes queued, processing, completed, canceled, and failed work. It should also give you a clear next step when a request needs attention.
Use free access as a way to test the workflow
A free-to-start plan is most valuable when it lets you test the parts that matter: source attachment, prompt control, output quality, project organization, and export. Current allowances should be read in the app because they can change by plan and provider availability.
Create responsibly
Only use media you have the right to use. Review generated outputs before publishing, avoid deceptive or harmful use, and follow the product’s acceptable-use rules.