When it comes to wordpress plugins, I prefer those that are free, easy to set up (even for those without any coding skills – my clients), and with as much as customization as possible.
When it comes to customization, you can change almost everything – that is crucial for websites written in other languages (or with sub-domains dedicated to different languages). And if you have some knowledge of coding – possibility of adding classes to individual elements within a form, makes it easier to target them with your css styling.
Besides all that, access to the stored data is well organized, and easily accessible – grouped by form through which it was recorded.
Of course, in regards to contact form mail delivery, it’s inevitable to run into a problem with the default php mail() function. Thus, setting up SMTP alternative is necessary more often than not. For this, I recommend using plugin named WP Mail SMTP by WPForms. It’s quite straight forward to set up, with the different mailing provider options (I’m using Gmail).