What JohnT said about CCA, and...
In all cases that I have ever heard of or seen study of, there is some kind of mis-use of the wood. Burning, burying, and others come to mind that are just opposite of common sense. A study done by University of Minnesota made raised beds out of CCA treated lumber and planted vegetables in them. They tested carrots, spinach, bush beans, and buckwheat grown in raised beds built with CCA-treated wood. All the beds were at least ten years old. Soil and plant samples were taken at varying distances from the wood border. In all cases arsenic levels were highest near the wood and dropped off quickly toward the center of the beds. Example: carrots grown next to treated wood contained 4 to 11 times the arsenic found in those grown four feet away. In their worst-case scenario, the Minnesota researchers found that a 132-pound person who ate seven ounces of spinach would narrowly exceed the daily arsenic limit established by the U.S. Environmental Protection Agency. Separate tests by the Connecticut Agricultural Station reached a similar conclusion: if you ate more than 11 ounces of fresh lettuce grown next to CCA-containing boards you could exceed the limit. The actual amount of arsenic in play here is minute — just 92 micrograms in the Minnesota example — and let's face it, even for greens lovers, a half to three-quarters of a pound DAILY is some serious spinach.
For Nova13, I suggest you read up on copper. You can be poisioned just as easily by that heavy metal as well. The .pdf you listed has some innaccuracies in it. For instance, the EPA says that no amount of arsenic is OK for children, but the article says that "the ESTIMATED amount of arsenic ingested by children who play on CCA treated wood is well above the EPA limit." Well, if the limit is zero, and a child goes out into the non-sterile world, then of course the arsenic that they are exposed to is "well above the EPA limit." You can't divide by zero and then make general statements.
Azole is a pretty potent biocide, even though it is organic. Borates, as discussed on this site, has toxicity to animals and humans when ingested. Quaternary ammonium compounds can make other health effects, like mild skin and respiratory irritation all the way to severe caustic burns on skin, coma, convulsions, hypotension and death.
One can even die from dihydrogen monoxide (the carrier for all these preservatives), which is at a much higher level in the backyards of the members of this site EXCLUSIVELY.
So, saying that one is better than the other, well, depends on the use.