Which is better: integrated graphics or separate graphics card?

I'm currently running Linux OpenSuSE 11.0 on a Dell Dimension 3000 with integrated Intel 865g graphics chip set.

I need more 2D display performance to use with the advanced desk-top effects available under the Compiz-Fusion package. I have an old, working ATi Radeon 7200 64 Mb AVIVO card. Will this card offer better performance than the integrated Intel chip?

What if I want to get better 3D performance as well - is the ATi card faster or slower than the Intel chip?

Overall, would the ATi card also result in a reduced CPU load?

Because my reading on various forums says that this sort of change can be quite error prone when performed by the inadequately experienced. I want to be sure it's worth while doing before committing between an hour and a month to recover!

My reading of the specs on the Intel 865G says it is probably much quicker than the ATi cards - which must be about 8 years old now, I guess.