U CAN compare the two, because essentially THEY do the same things. Now comparing an iPad to a lap top isn't right.
It's about speed, ease of use, portability, gaming, screen real estate, and network reliability. The iPad kills 50% of the list(ease of use, gaming, & screen real estate) do these three areas outweigh the other three? Only u can decide that my friend. Let me say though, the iPad is not slow by any means, it is very portable, although u can't pocket it, and the networks bad reception is over exaggerated AND DEPENDS ON WHERE U LIVE.
I use to own an iPhone. Sold it recently because I don't talk on the phone(refuse to pay for minutes i dont use)and I have an iPad which does the same things it does(before iphone4). Now I'm gonna buy a boost because it's just cheaper. Probably won't need the boost after a while because VOIP apps. Just waiting multitasking and push. I know how to be patient.
Now if you are a recording engineer, artist, or u do some type of work where being able to transfer information from iPhone to iPad to Mac or something, it's a whole other story.