What's the best joinery method for cabinet face frames? That may seem like an simple question, but actually it's a hotly debated topic among professional cabinetmakers, who have an equal interest in making a product with solid joints and getting cabinets out the door fast.
For the hobbyist, who has much more freedom to experiment, it's a slightly different story. If your livelyhood doesn't depend on getting things done as fast as possible, then the choice really depends on the conditions the cabinets will have to face, skill level, the equipment you have available, the amount of time you want to devote to a given project, and your particular conception of the term "quality workmanship".
In a large part, it's a matter of woodworking philosophy. Some cabinetmakers just seem to prefer time-tested joinery methods, and may go to the length of cutting a bona fide mortise and tenon for every face frame joint. There's little doubt that this method is the slowest, but there's also no question that it produces the strongest joint. Most would argue that structurally, a mortise and tenon joint verges (at least) on overkill in this application, but if you're dedicated to making cabinets in the highest possible craft, that's probably the way to go.
Or you could consider a compromise: If you're committed to idea of building cabinets suitable for centuries and centuries of use, but would prefer to move along a little quicker, you might consider one of the methods that are the structural equivalent of a mortise and tenon joint, but a lot easier to perform. The affordable BeadLOCK system is a good example. The BeadLOCK's "loose tenon" joint is arguably every bit as strong as a mortise and tenon joint, but takes considerably less time to make.
The Festool Domino Joinery System is essentially a loose tenon system, and makes the process as slick as it's ever likely to get. The Domino is making a big splash among woodworkers of all kinds, with its mix speed and an extremely durable joint. It's a little more money, but if you plan on being in the cabinetmaking game for a while, like to speed along as quickly as possible, and prefer a joinery method that will leave no questions surrounding the integrity of your face frame joints, the biscuit joiner-like Domino System is impossible to beat.
On the other end of the spectrum, you'll any number of cabinetmakers who swear by the speed of pocket hole joinery. Pocket hole joinery is used widely in the cabinetmaking industry, and by all accounts is the clear winner when it comes to getting through the face frame assembly process fast. Pocket hole joinery won't tie up your clamps and has the added advantage of making your face frames fairly easy to disassemble, should the need arise. While pocket holes are no match for mortise and tenon joints in strength, most cabinetmakers find them more than equal to the task of holding together a face frame, where joint stresses are relatively low.
For the hobbyist, the name Kreg is synonymous with affordable, easy to master pocket hole joinery. Over the years, Kreg has continued to improve its groundbreaking jig, and now offers a number of kits. Starting at under $15 and ranging up to around $140 for the K4 Master System, Kreg jigs are available for virtually every woodworker. And down the road, if you decide to turn pro - and thereby outgrow the manual jig - the semi-automatic Kreg Foreman will bring you up to production speed.
Still other cabinetmakers prefer to dowel their face frame joints. Nothing wrong with that: Dowel joints have been around for hundreds of years, are more than strong enough for a face frame, and as long as you own a drill, require only a minimal investment in a doweling jig and few dowels. Biscuit joinery is yet another option for owners of the Porter Cable Biscuit Joiner, which comes with both a standard sized blade and a smaller FF biscuit-sized blade. Both methods have the advantage of "automatically" aligning the surface of the joint.
And there's plenty of room to experiment. None of the joinery methods mentioned here are limited to face frame assembly, of course. All can be used in a wide variety of woodworking situations. In other words, buying the equipment necessary to try one or more on a specific project involves very little risk - if it turns not to be the preferred method in one situation, you will, without a doubt, find a use for your newly acquired joinery technique somewhere else.