I am trying to create a DIY wide angle webcam with the goal of maximizing my horizontal and vertical fov. I'm thinking that I need to use fisheye filters and then defish the video afterwards. Is this worth the hassle vs just getting a wide angle filter?
The field of view would be the same as an equivalent focal length, but fish eye can go wider than a flat lens. There is only so much distortion you can remove however. By nature of the way the light paths travel, there is going to be some roundness to the image. It's the same problem as projecting a round globe on to a flat map. You can distort the image to make it appear less rounded, but this actually decreases the accuracy of the image because the angle that things were photographed from was not flat, it was rounded. This means that on the edges, you will be making it look like you are looking forward at things you were actually looking sideways at.
It's also worth noting that even non-fisheye wide angle lenses do a certain amount of this effect as well, it is simply projected differently.