Forms With Custom PHP

Hi guys,

We are in the process of redeveloping our site with Wordpress. We have lead generation forms we use that has custom PHP code that routes the form results to the correct email based on an ID code.

What is the best suggestion for using forms with custom PHP in Wordpress? Should I use a plugin like Gravity Forms or Contact Form 7? Should I hand code a form without using a plugin? Your suggests are greatly appreciated, thanks!