Been MDing for about a year and a half with the Prizm. First I will tell you what I have experienced (pro's), although I am still new at detecting. It is light and I can detect all day with it, I can see its LCD display with sunglasses on, I like the tone ID, Pinpoints very accurately, also its target ID is very accurate, the depth readout is pretty accurate, it is very easy to learn (and I can tell you some of its behavior on certain targets, if you purchase one), and it has good battery life.
Bad...well it runs very silent (good in someways) there is no threshold hum as I have found in my beachunter ID. There is no way to hear what others refer to as faint signals. I think this may be why I have never dug a coin deeper than 3-4 inches. I have not dug an old silver coin yet, and I have detected 150 year old farm house and a 144 year old Victorian (exclusive permission on the vic), and numerous parks. I think the notch disc is a waste of space, I do run the disc to take out iron though, that is maybe why I am lacking depth?
Overall I think it is a great starter, and I can go out and really pull out the clads in a park. I have been able to find 14 rings with it so far. No real expensive ones, just sterling and one white gold class ring (which was my first ring ever

) The price is very reasonable too, and if you check ebay you maybe able to find a nib one for less.
I have not tried the Garrett although they are a good name and two friends of mine use the Ace series and love them.