The brightness is about the same as my iPhone 5, but the display is much larger which makes everything easy to see. It's somewhat brighter than my old compaq pocket pc.

However, it need to be mounted so that you're viewing it close(ish) to vertical. I tried the iPad sitting on my leg, and I couldn't see anything. But when mounted facing me, it was great. It does not need to be at exactly 90 degrees, but laying it down on your leg (while you are reclined) doesn't work.

Another thing about the iPad is that it allows for 8 info boxes across the top and another 8 across the bottom. With the phone I got 8 total. Also the menus work better on the iPad.

If you go with the iPad, you'll need the cellular version. Or you can use the wifi only version with an external Gps. You don't need cellular service, just the cellular version of the iPad.