Is there a field limit on JotForms?

 Wufoo has a 100 field limit, but I need a form builder with more flexibility for large forms.

No, there's no known limit for number of fields in form. You may create as many as you need. However, please note that the greater the form is, the more time it can take to load it in browser. You can still try if it would work good enough for you. Just in case, you can always split the form into 2 or 3 smaller forms and redirect users to next form automatically: Redirecting-Users-to-a-Different-Page