Pascal said:
that said, anchoring technique is usually far more important than the type of anchor. deployed properly most anchor will set and hold; the problem is that so many boaters are very good at screwing up something as simple as anchoring!
Right on, Pascal. And if you really care about the set and want to sleep well, like you said earlier in another post, you swim down and eyeball it and hand place if necessary.
thoward, you asked about whether those light Fortresses "sail" on you in a light current. Yep, they will if you let 'em fly; when using a Fortress, I always feel better about paying them out more gradually. Conventional Danforths will do the same, just to a lesser extent since they're heavier.
All the Danforths are prone to clogging up with weeds and have difficulties penetrating matted grasses & weeds. The Keys are notorious for that down around here. I can't count the number of places down there that have a hard flat bedrock coral bottom with the thinnest skim of silt & some fairly thick woven weeds thatched across the top. Your best Danforth type will just claw a trough through the weeds and won't grab anything. It's really maddening when doing inshore fishing in a small boat and trying to find ANYWHERE around a cut or channel that you REALLY want to fish where you can get your !@*#$ anchor to hold!

In a bottom like that, I'd have to think an upright plow like a Delta would work the best -- you have one sharp point that could snag SOMEthing, and it wouldn't foul from the weeds.
I've got to second what Pascal had to say about Fortresses when they take a good set in sand or muck -- you need a bulldozer to break them back out again. Three hurricanes here over two years made me a believer. I'm gonna guess a high tensile-grade Danforth would work really well in that application, too. Truly, after seeing them work in those kinds of extreme conditions, I now honestly put more faith in the hold of a well-set Fortress than even the stoutest cleat anchored to a seawall on the other side of the canal.
Moral of the story? Add my name to the list that says having at least 2 different styles of anchor on board is the way to go. Who knows what kind of bottom you're going to run into.