Gnarly Head's zin is one of my favourite, moderately priced zins ($16-17 here). I describe it as an "in your face" red fruit (jammy) wine with modest tannins. A very versatile, easy drinking wine. If you are looking for a zin that might exhibit a modest difference from decanting (I'm in the "decanting makes a positive difference with reds" camp), I think the Gnarly Head would be a good choice. If you are looking for a zin that is more likely to be affected more obviously I'd recommend a zin with more tannins like the Four Vines "Old Vine Cuvee" zinfandel ($20 here). To my pallet it's more reserved than the Gnarly Head with smooth layers of black berries and a hint of spice (probably pepper) and its taste changed more from glass to glass.

I look forward to reading about the results of your experiment.