Advantages of a balisong?
It's fun to play with, can be shown off to friends even if you don't have a really good one due to how different it is from other knives, often have more reach than folders, has a thinner blade that can get into spaces that folders or fixed blades often can't, and has a strong lock.
Disadvantages?
They require more room and effort to open than more traditional folder designs, a fan switch from a forward to reverse grip needs it to be latched closed, things like the Axis lock, Rolling lock, or a number of other newer locks are probably stronger than what often are cheap pivot pins, the handles are probably more prone to slippage than a folder that has a finger guard or textured grip, blade types are more limited (ie no hawkbills), can garner negative reactions, and serrations on one are a bad idea due to a higher chance of cutting yourself with one and the serrations leaving a slower healing wound.
There's not much a bali can do that a folder can't in terms of utility or defensive use aside from handle flails. Folders can be used as kubotans in their closed position just as much as balis can.
My suggestion? Carry more than one knife around. At least one plain edge folder or fixed blade, a serrated folder or fixed blade, and a bali for the thinner blade and to have fun with. If carrying that many knives isn't really an option, you can decide what option would work for you based on the pros and cons.
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Simon Yu
"I look at it this way. If things get much worse I'll be too dead to care."
