I have HomeAgain in my pets. The vet clinic/shelter must have a scanner that can read BOTH types of chips, as they are different. Otherwise, if they have a scanner that only reads one type, it's like your pet doesn't have a chip.
Yeah, no kidding, Riley! Our vet clinic just got a scanner that can read HomeAgain, Avid, and international chips (like if you live on an Army/Airforce base, all animals must be chipped). I guess that model is pretty new, but is cheaper than having up to 3 scanners!
I have both, the vet did Avid in my snowshoe kitten, and the breeder put Home again in my 2 Siberians. So I don't know that either are better than the other, I just think it's great to have such a thing these days.