Yeah, you'd have to pay extra to upgrade the video card to really put the Pentium to use.
Unless you are a hardcore gamer or something, which is probably not the case because most of them seem to be hardware nerds, just go with the Celeron. Pentiums could be considered THAT much better than Celerons but that is because they are designed for different purposes. Unless you need it to do engineering work or drafting or something, there's no compelling reason to pay the extra money unless you just want the best of the best.
I have the same Celeron processor right now on my laptop and it's great. I never have any problems with my laptop. My connection is always top notch and my computer doesn't lag at all, unlike the desktop PC which is the families and probably has countless amounts of spyware all over it. One of those computers that take 5 or 10 minutes to actually boot up. Mine takes maybe 10 seconds. The biggest thing is to keep your system clean from viruses and spyware. With getting a new system, I can't stress that enough. If you get good protection and are smart about what kinds of sites you visit, you can make the computer last a lot longer than most people seem to do.