Hi Scott,
This is a bit like asking, "What is the best car?" It depends on the needs and the budget. After years of testing and using many different proofing papers the issue for me breaks down to a few criteria.
1. Color: must be bright enough and BLUE enough to simulate the brightest and bluest press substrate you need to simulate. Assuming we're discussing inkjet proofing, press substrate color can be simulated, but there are limits to this as the dot added to the background to adjust its hue will also darken it, and this can be a more visible error than the hue difference. Bluish proofing papers have an easier time matching warmer press stocks than vice versa as mostly yellow dot is added, which barely affects the L* value (warmer stocks are also generally darker, further easing the difficulty of the match). To match GRACoL or Fogra 39 (95 0 -2) you should start with a proofing paper that is at least 95 L* and at least -2 b* (a* is usually close to 0 in proofing papers) but can be as much as -4 b*. If you're using an HP Z31/3200 the Gloss Enhancer (very nice) will reduce paper brightness by about 1 L*, so with these printers start with a brighter paper, perhaps 96 L*. If you go higher than that you'll probably be using a paper with excessive levels of optical brighteners. I'd say the same with any paper bluer than about -4 b*. Avoid "photo" papers that are not specifically designated for proofing as they are often loaded with OBAs. You can test with a UV black light to be sure.
2. Ink limit: The paper needs to accept enough ink to achieve the target gamut on your printer.
3. Surface characteristics: Gloss differential should be minimal with the ink you're using.
4. General look and feel. This should bear some relationship to the press substrate, but only general. Satin proofing papers can be used for both coated and uncoated simulations and are thus the most versatile. For newsprint I would use a real newsprint proof paper.
5. Cost. Remember that only a few mills make proof papers and that many high-priced media sold by printer and RIP manufacturers are available in "plain vanilla" packaging from paper converters such as Mid States and Alameda. Compare specs and ask for samples for testing.
Be wary of recommendations made by anyone insisting that one particular paper is "the best." Remember that RIP and printer manufacturers are skillful at creating print environments (ink limits, linearizations, profiles) that exploit their own media's potential and may have no interest in making other papers look as good. The only way to judge a paper's quality and suitability is to calibrate the RIP and printer correctly for it, and few users have this knowledge and skill. Most find it easier to use the "recommended" paper and proclaim it "best," which for them is actually true.
Disclaimer: I myself sell EFI Validation Media and Mid States proofing papers, so these recommendations are not brand-neutral. I really like EFI Validation 250 Satin and Mid States White Satin 230 and Semi Matte DP for general-purpose proofing. The quality is high and the cost is reasonable. Alameda also has some attractive papers at a good price. Kodak, CGS, and GMG papers can be excellent but are expensive. Be sure that your paper supplier can provide the advice and/or complete print environments for your paper, printer, and RIP or that you have the skill to make such environments yourself. If your media reseller can't help find another one.
That's about it.
Mike Strickler
EFI Bestcolor certified implementer
Idealliance G7 Expert
