Which Multi-language option for WordPress is best from an SEO and Woocommerce perspective?

If you need true localization, like a different checkout process, different themes or product descriptions, then you should use a multisite. You can activate plugins and themes per site here.

The problem here is that almost all shopping plugins are not multisite compatible. You have to activate them per site, not as network plugin, or you won’t get the required database tables.

The custom tables are also difficult to translate. This cannot be handled in a regular plugin, because that would create too deep dependencies. So you need an additional plugin to fill the gap. Inpsyde/MarketPress, the company behind MultilingualPress, has a private beta version of such a plugin. You can contact them and ask for an invitation to the tester group.

Disclosure: I was the lead developer for MultilingualPress for more than two years, and I wrote the very first version of the compatibility plugin for WooCommerce.