I used to be under the impression that antiperspirants and deodorants are the same thing, but they're not. Antiperspirants use strong astringents like aluminum salts to clog, block, or close pores so that they can’t release sweat. (Studies have been shown that aluminum can accumulate in the brain and may be linked with Alzheimer’s, among other things.) Deodorants instead neutralize the smell of the sweat and also by using antiseptics against bacteria. I think deodorants are better (IMO) because they don’t keep you from sweating. I think sweating is important for cooling, especially on a bike.

Personally, I have used the crystals and have found them to be pretty much ineffective. If I have to use an off-the-shelf deodorant, I get Tom's of Maine or Nature's Choice, whichever is cheaper and whatever styles (smells) they have that I like. Both seem to last longer than conventional deodorants (while not costing a great deal more) and seem to work (for me) very, very well.

As of late, though, I've been making my own homemade deodorant, and the results of it's effectiveness has been surprising. Actually I made two different kinds, one with baking soda as the main ingredient and the other that was a gel and used witch hazel and aloe vera gel. Both formulas used lavender oil, which has natural anti-bacterial properties. Both formulas have also been working great, as good as any name brand and significantly cheaper, especially since even a small batch can last almost 6 months. When traveling I've been using the small plastic travel shampoo bottles to store the gel, and a small Tupperware tub to keep the powdered stuff. Normally if your ride is short and you have a restroom at your disposal, all you really need to do is splash your pits with some soap and water, dry, and put on some deodorant.

When I used to ride to work (now I work from home) I wouldn't put on deodorant before the ride at all. Supposedly for long rides, stuff in your pits traps sweat and is eventually overcome, so your pits are smelly anyway. Plus you don't have stuff in your pits blocking any cooling action going on.

Nowadays, if I have to run an errand or something on the bike it's not a terribly long distance so this isn't really an issue, and even in this hot steamy weather the homemade goo is working surprisingly well.