I've had the garmin units side by side with the Magellan units and the Magellan always had better signal. Just my observation. I use an OLD Magelan unit with very few bells, no whistles, and no PC interface. The key is knowing your unit and practicing with it.
For a pack strap holster, I use one of those leatherette type cigarette pack cases that has a belt loop on it. I just add a velcro loop thru it's belt loop and around the adjustment web on the shoulder strap. I never carry anything hanging from my neck because if I fall, that will be the first thing to hit the ground. Look for the cigarette cases in the dollar store or perhaps Walmart, you might also find an eyeglass case that will work. The cigarette cases are also great for small 2-way radios. If they have a zipper top, like mine does, they allow for the antenna to poke out of the top.
My only complaint about the Magellan I have is that the darn backlight keeps coming on when the button is bumped, that causes the battery to die quickly. I never record my tracks, so it doesn't matter to me. I do however mark important waypoints like springs not on the map and record them when I get home.
One further suggestion is to keep an eye on Ebay, buy a basic one and learn what you like and don't like, then go get the one you want.
Lastly, I've gotten in the habit of printing out maps with 5 second grids on them of the area I'll be hiking in. (I create these from USGS topos in AUtoCAD). It's kind of fun to be able to see exactly where you are on the map and also practice guesstimating how far to the the next junction or land mark. I make a game out of it, and it has improved my skill greatly.
(No, I never go out without my Silva either!)
Tom