Rusty....you are correct. There is no difference in protection between the SPF's, as long as you stay at 15 or above. You'll just be applying it alot more with the lower numbers....and who wants to do that...?? I use an SPF 45..and reapply every 2 to 3 hours...whether it's sunny or cloudy, that's more than is really needed, but since I already had a melanoma, I'm now 50 times more likely to develop another one over someone who has never had one. So I slather it on quite liberally.
Whatever brand you choose, just make sure its a broad spectrum protectant...meaning it blocks out both UVA and UVB rays...both are damaging and potential killers. Depending on where it rears its ugly head on your body, melanoma can potentially metastisize in less than a year...once it does, it cannot be stopped. Fortunately, for me, mine was caught and removed just in time. I cannot stress enough the importance of finding a good dermotologist and seeing them annually, especially for us outdoorsman. I must go every 6 months.
By the way Billy, the Neutrogena is available at most drug stores in the sunscreen section...no need to go to any department store make up counters. $30 bucks for a tube of the stuff I mentioned....I use 4 to 5 tubes of 45 SPF a summer, then drop down to a 15 during the winter months (I wear sunscreen everyday, even if I don't plan on spending time outdoors, just a habit now).
One thing I forgot to mention, was the importance of quality sunglasses. They too should be broad spectrum UVA and UVB protected. As nasty as it sounds, skin cancer (all 3 types) can develop on and in the eye just as easily as it can on the skin.
Take care of yourselves my friends...I ignored the warnings for too long and payed the price with a literal scalping of my forehead. U definately don't want what I had. Perhaps I'll post some pictures of my surgery (a plastic surgeon friend of mine did the work), they just might scare all of you enuff to turn you into summertime grease balls like myself.