I have a PRC-3 and its works fine; the 4 also does the job well. You won't go wrong with either.
The key to getting records clean is not the difference in strength of the vacuum pump between the PRC-3 and the PRC-4.
The key to getting records clean is:
* the fluid used (AIVS for me),
* fluid application technique (brush lightly, don't scrub),
* most impt. the amount of time the fluid is on the record,
* and lastly, a pure water rinse.