• The number of customization items and their features
• Total control over the construction of the form, and 
• How to create.

The editing and PDF features are the most valuable features. 

The "import from PDF" has been a lifesaver for our company. It allows you to upload an existing PDF form and it automatically creates form fields for you! (It's not perfect but still surprisingly accurate). These are all available in the free plan, you can choose the higher tier plans which allow for more forms and submissions. 

If you dont have an existing PDF you can just build one yourself with the PDF designer. Although, I found the builder still a little underpowered in terms of flexibility in the design and positioning of the fields. 

I have found many useful features.

The most valuable feature is the ability to create different selections for different text-fields. The IF condition allows us to show or hide text-fields based on our requirements, and the functionality is extremely useful.

The Advanced Form has all of the important features existing the in JotForm.