Well, depends on what you want.
Will you use vari-volt? Consider whether or not you ever have a desire for more power adjustment than standard 3.7v, or 3.7v with an LR, or 5/6v will offer. If so, then you may want vari-volt.
The price of vari-volt, to me, was in complexity. Complexity almost always means a shortened life span. Now, lots of people have had their Buzz's keep on truckin' through even the worst treatment, so I'm not saying that these types of mods are necessarily failure-prone. It depends on how they're built.
But, for example, when hunting for a mod I decided I never wanted to buy another mod again, and vari-volt didn't matter to me. Thus, I could narrow the playing field down to all-mechanical mods, which have the longest life expectancy.
Going with a quality vari-volt like the Buzz (and they're coming out with a sleeker vari-volt called the Infinity soon as well) will probably offer you lots of longevity as well. But it just depends on what you want and need.
What do you want from a mod, in terms of features, battery life, over-all life expectancy, versatility, size, and cost, and how do all those things balance out with each other?