Mosfets vs. Buckpucks in driving high power leds
BuckPucks are a branded retail product. Internal to the BuckPuck is some proprietary current-regulated circuit, which undoubtedly contains resistors, capacitors, transistors (MOSFETs and/or BJTs), diodes, and probably many other components and ICs.

MOSFETs are a type of transistor and are a basic component of electronic circuits. They do nothing by themselves and require a good understanding of how they work to successfully incorporate them into a design.

Here's an analogy: A BuckPuck is like buying a Honda Civic. It's a fully functional system made up of many many parts. A MOSFET is like a piston in the engine. It's just one component of a much bigger system.

You'll definitely want to use a constant-current regulator to drive your LEDs. But there are literally thousands of ways to design regulators, many of which use MOSFETs. Some designs are more robust or cheaper or more flexible or use less parts or use more parts. There's no one way to design anything in electronics.

It sounds like you stand at a crossroads. You can choose to drop 50 bucks on some BuckPucks (or any number of other pre-packaged LED drivers on the market). Or you can learn about electronics design and figure out how to make your own. The former is quick, but you're forever limited to what other people have already designed. The latter is long, grueling, but incredibly rewarding.