There are many advantages to kettlebell training. The RKC uses them primarily for strength. Power lifters use them as a form of cross-training, while strength and conditioning coaches will use them for athletes in need of additional metabolic conditioning. What's "best," however, depends on your training goals. For the purposes of fat loss and general cardio, there are two strategies you can use to maximize results.
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This is a form of circuit training consisting of three to four exercises. Each exercise is done for five to 10 reps. The circuit is performed for time. For example, a density circuit of the swing, push press and pushup would be performed at 10 reps each for 10 minutes with as few breaks as possible. After a few weeks you would progress to 12 to 15 minutes. In another month or so, you would go up to 20 minutes. The weight should be moderately taxing, as the time itself will provide the real challenge. This is an effective choice if your focus is fat loss.
Ladders are progressive descending or ascending sets of exercises done for time. For example, if a ladder of power swings and goblet squats is written as "10-9-8-7-6-5-4-3-2-1" then you would perform 10 power swings followed by 10 squats immediately followed by nine swings and nine squats. You would repeat this pattern until you finish. Like density training, rest only as needed. Most ladders should be accomplished in 10 minutes or less. This makes a great cardio challenge and an smart choice if you're pressed for time.