On the down side for the TaP, though, is that it is smaller (1.6 gallons instead of 2.3 gallons), it is more expensive ($80 each instead of $40).
On the good side for the TaP, the CO2 cartridges are cheaper, usually a 10-pack costs like $7 or so, I think, which will get you through a couple of gallons, where as the Party Pig pouches are $5 each. Another positive is that the TaP dispenser will fit on 3L soda bottles in addition to the 6L bottle that is ships with, which I suppose would be useful in some instances.
I know when weighing the pros and cons a little over a year ago I went with the Party Pig, and overall I am happy with them, they are pretty easy to use and easy to clean, and I havent perfectly nailed down the amount of priming sugar required yet but I am pretty close after using them for 4 batches (really only using them twice, though, as each time I used them I did two batches in the span of days). HOWEVER, I realize that I would just really appreciate 5 gallon kegs a lot more, it would make my life a lot easier, and so that is why I am saving up for those...