I had my last yorkie tattooed..... this was like 15 yrs ago. Before chips were widely used. I had it done during his dental. It was on his belly - beside his "tee-tee"

It was my social sec #, I had it registered with an agency....I don't really remember the details. Thankfully I never needed it. It never bothered him, it did fade and smear over the yrs and was unreadable.
Personally, I think the chip is better and easier to use. If your dog is lost, the chip can be read by SPCA, vets, ect.... the tattoo would have to be researched somehow I'm guessing????
just my 2 cents....