What camera has wider lens, 28mm or 30mm?

Which is the one to get that is wider and better???

The 28 mm lens is just barely wider. It would probably be hard to tell the difference without examining the edges of identical pictures. A 14 mm lens would be wider. If you get an extra wide lens it's called a fisheye.
It's hard to say which lens is better without knowing the f rating of the lens and the quality of the optics.
I don't know if that's really what you're asking, but I hope it helps.

if these are 35mm FILM cameras, then either would be considered to be a wide lens. The normal focal length for film cameras is 50mm, but in recent decades, shorter lens have been used because they are less expensive to produce and make focus a non-issue. if these are on a Digital camera, then they are not wide at all. That is because the image size of the CCD is less than 35mm film. In some cases it is only 1/10th the size and that would make even 28 mm a very telescopic lens.

However this concerns focal length. If by 28 or 30mm you mean the filter attachment diameter for an add-on aux lens, then you need the size that fits, the diameter does not affect the angle. These are usually 0.7 x magnification, but fish-eye type with 0.4 x magnification are popular for video cameras shooting skateboard or other similar action, mostly because they eliminate the need to focus, or even aim.