In Australia if you are a member of Dogs Victoria (I dont know what your governing body is called in the us) and you mircochip your dog you get a discount from the vet
! You also get a discount on registering your dog with the council (all dogs over the age of 6 months need to be registered with the council or you get a huge fine). The chip is quick and painless (well none of my dogs moved when they got done) and costs around $50.00.
One the off chance that your dog is ever lost and impounded, the animal shelter will scan the dog for a chip. Your name and number will come up aganist the chip so that you be contacted to go collect your dog. I am not sure if this happens with the tattooing?
Haven't ever had my dogs tattooed so i cant give any input on that.