So, I'm a few years late, but had to challenge HanP's post because it appears first on google. I've been using MSP since it came out and Prima Vera since 1997. I've included a few jpgs to illustrate my points.
"1. Only single relations between 2 act's, so no SS/FF possible in MSP."
Simply not, and never has been, the case. Unlimited relations and all types are supported.
"2. No S-curves or complex Histograms in MSP."
There are S-curves but they are rubbish. Complex histograms also not possible.
"3. Early/Late calculations not present in MSP."
Not the case. MSP has always been a PERT based program.
"4. Only one baseline(target) in MSP, 2 in P3."
Not the case. There are in fact 10 baselines in MSP, and you can define more using the customisable date fields.
"5. Exchange with MS-Office products is better in MSP."
True.
"6. Microsoft look-and feel and use of macros is an advantage to MSP."
Visual Basic is even better. Interface compliant design in MSP is also a bonus.
"7. Better use and more codes in MSP than P3."
True.
"8. Probably more developments for MSP than P3."
Very true. 2003 pro is the first planning package I've used in 10 years that feels like an imrovement over Open Plan's functionality. Project 98 is perfectly functional though.
"9. Percentage relations in MSP, not possible in P3."
Yes, they are.
"10. Outline / structure options in MSP better than P3."
True.
Some other differences.
P3 can't handle cost assignments above a certain number of millions, a real pig to handle if you are using Roubles or other low denom currencies.
P3's output is superb, though fiddly and sometimes unflexible.
I have never managed to get p3 to handle documents including both cyrillic and latin text. MSP does it without any differentiation.
Project 2004 Pro will read straight from your Ms Access (or SQL) databases. This is a big deal if you are running a CTR or Jobcard system.