Is SPF 50 better then SPF 30?

From the Journal of The National Cancer Institute:

According to Weinstock, the cap on SPF labeling is not a major issue for the public as a whole. "I think that if the general public uses SPF 30 or greater, that's sufficient." As Weinstock explained, SPF is a reciprocal function: SPF 15 lets in 1/15 of the burning rays; SPF 30 lets in 1/30; and SPF 50 lets in 1/50. Therefore, the difference between SPF 30 and SPF 50 is only a difference of 97% effectiveness versus 98% effectiveness. "That little bit may be important to some people who have particular sensitivity," said Weinstock. "But, to the general public, it really is not that critical."

Remember that SPF30+ sun cream will block out 97% of the sun's rays. SPF50+ will block out 98%. There is NO bearing on the DURATION you can put the sun screen on and expect protection.

The issue is that people generally don't put on enough, so they're only getting around 50% protection because of their own vanity. The more you put on, the closer you get to the full coverage offered by the cream. If you use an SPF30+ cream you'll only get a little less protection than the 50, but you need to use enough. The SPF isn't the issue, it's the usage.