Before reading the responses I actually took screenshots to prove that the keyboards in Mail and Safari are the exact same size.
But after reading I realize you are referring to the landscape keyboard.
…which I never use. I type very fast with my thumb. (challenge ya to thumb wrestling!)
But yeah – I almost never use landscape mode for browsing unless it is early morning and I’m still in bed, or if the website just really sucks in portrait mode. (I use my iPhone for browsing like 5–6 hours out of the day).