Careful, scooters are like crack... I have two used Makos (paid $1000-1100 each + new batteries, ~$80 per set), they are fun as hell, like others mentioned they use basically the same "drivetrain" (shroud, prop, motor, clutch assembly) as Gavins, SS. The big difference is in the physical build (Mako = thin plastic), and size/buoyancy. The Makos seem to have been designed around a light set of batteries, relative to what most people use these days. So the Mako will likely end up being a little more negative than ideal, especially in fresh water. The SLA batteries (they use 2 12v batteries in series for 24v) are cheap which is nice, low cost of replacement and it's affordable to have a second set to swap between dives. The Mako is rated at 180 foot, if you're just doing recreational diving, and don't mind the size, they are a good value and tons of fun.
The X ($3500 ish) scooter is very different in that it uses a brushless motor w/ electronic speed control - newer technology, some say that due to the complexity it could be less reliable than the older brushed motor used in Makos, but that doesn't seem to be borne out of experience w/ the X from what I've heard. The X also uses NiMH batteries, w/ Lithium Ion optional. Advantage is power density, so you get about the same runtime in a lighter and therefore smaller package. They also sell the X with a hard case that weighs I think just a bit more than 50 lbs which makes it good for air-travel. I would love to get an X scooter, to take on vacation, and while I haven't used one I understand they are a little faster than a stock Mako. A second battery to have on hand is pretty pricy, around $500.
SS makes a brushed scooter with NiMH batteries as well, I think the cost is similar to the X.
You can also get a Tekna for about half the cost of a Mako, disadvantages would be the batteries for all practical purposes are not swap-able between dives, you'll have to recharge. They are also smaller, so will need lighter batteries, and will be more negative. They have the same prop/clutch/shroud, and more or less the same motor as a Mako, you could probably get a running unit for 5-600 and it would be a ton of fun.
The Sea Doos and other 12v geared motor scooters really are not in the same league as the Tekna/Mako/SS/X. I haven't used one but I've heard they are faster if you kick while using them
On the Makos, forget about trying to kick, if you do anything other streamline your feet, you'll slow it down. I do have one though, new in the box (never used it since I got the Makos). It's yours for $100 + shipping if you like. Deco Stingray, it's the same as the Sea Doo classic that sold for $280 @ Leisurepro.
Rob
