tbh it's likely no different from ordering threw your local LFS unless you know your local has a good supplier. I've never ordered anything threw petco special order, but when i worked for one i wasn't overly impressed with how the fish came in ( that may have changed in the past 6 years, idk.) If your local petco gets in nice fish.. it may be worth ordering threw them vs online ( you won't pay shipping fees as it will come with their order) so you may have to be able to pick up the fish at say 3-4pm on a thursday or whatever is their shipment day ect...
personally i like to visit the local shops on their fish days and see what quality the fish are the day they come in. if they consistantly look poor, I usually buy my fish elsewhere..
