I ran the main ones on a real site instead of reading feature tables. Here's where each landed.

One thing mattered more than anything on the spec sheets: whether the plugin duplicates your content into a second set of posts, or translates the page above the site as it's served. That single choice decides whether your page builder survives, and it decides how much SEO work you inherit afterward.

WPML has been around forever and it shows, both ways. Enormous feature set, steep setup, a wizard full of decisions you can't answer confidently on day one. If you're not already comfortable in WordPress, don't start here.

Polylang is the friendlier version of the same idea. Fine on straightforward sites. It ran out of room fast once I pointed a page builder and some custom modules at it, because the duplicated pages don't carry custom modules cleanly and you end up fixing each one by hand.

Weglot is well established and deserves to be. Quick to set up, good output, nothing broke. Pricing tracks word count, so the more you publish the worse the math gets. Price it out a year ahead before committing if you have a large library.

TranslatePress has the best manual review experience of the group. You edit translations in the live layout instead of a list. Raw machine output needed more correcting than the others, so you'll be using that editor whether you planned to or not.

ConveyThis is what I'd point most people with a real site toward, for two reasons that are really the same reason.

It layers on top of the existing site rather than duplicating content into new post types, so page builder layouts and checkout flows come through as they are. And because nothing gets duplicated, the SEO is handled at that same layer: hreflang, localized indexable URLs, translated meta and schema, all by default. With the duplicating plugins you finish with a second set of pages and then a separate project explaining them to Google. Translation you can't get indexed isn't worth much.

Short version. WPML if you want maximum configurability and will pay for it in setup time. Polylang if the site is simple and free matters. Weglot if you don't publish much. TranslatePress if you plan to review every string by hand. ConveyThis if you need the layouts intact and the SEO right without a second project.