Hugelkultures benefits are many: eliminating or decreasing the need for watering and tilling, sequestering carbon, increased nutrient retention, increased soil OM, increased vertical growing space, increased fungal life, micro climate creation, blah blah blah. Chances are, if you have stumbled across my blog, you already know about the bad-assness that is hugelkulture. The one and only con of a (properly made) hugelbeet is the upfront labor required to create it.
Just how much labor is required? I once read on permies.com that the work expended in establishing a hugelbeet is equivilent to 5 years of labor condensed into one. Creating mine by hand, i feel that this is about accurate. Keep in mind, your milage may vary. I'm a 24 year old professional athlete so hauling logs and slinging dirt is one of the less physically demanding exersises I regularly perform. But even my grandma could build a huglelbeet if she had a tractor and any incentive whatsoever. My hugel beds are sunken, which means the dirt on top comes from the adjacent section, as opposed to being hauled from A-B which would be much more laborious. The logs im using come from a giant brush pile that is conveniently located about a football fields distance from the mounds ive been building. If your source of wood is further or closer, your project will be more demanding.
Most of us after reading the previous paragraph can agree that in my particular situation I have it much easier than the average bear. But on top of the relative ease or my situation, I have far more incentive than AJP (Average Joe Permie) as well. The rainfall around here tends to swing from one extreme to the other. I kid you not when I say that 2 weeks ago we were digging a drainage ditch to save the veggies from drowning but are now furiously pumping water into the field to keep them from drying out. The soil we have to work with is pretty high in clay which means it both drains poorly and presents lots of resistance to deep root penetration making veggies grown in it especially sensitive to excess and inadequate percipitation (though the quack grass does just fine). Hugelkulture provides a buffer against rain extemes by lifting the veggies above the muck, providing soft, easily penetrated soil to burrow into and high water retention. That's what we professionals like to call a "win-win".
On a side note, green vegetables can triple in price immediately after a typhoon. Having some leafy greens chilling on top of the hugelbeet immediatly after Mother Nature throws one of her infamous tantrums provides some economic opportunity. Cha-Ching!
Deciding wether or not to give your field the agricultural equivilent of breast implants is not an issue of pro's and con's. There simply aren't any con's aside from the upfront labor. It is deciding how much labor, in your case, it will take to make hugelbeets compare to how much labor it takes to manage your field without them, and how badly you need the buffer against rain extremes.