there is clearly no BC in Runner lol between barbie collies and aussies, even I have a really hard time telling the difference and I mix them up all the time. however with real BCs and aussies, the difference is very clear:

BC:
tails
longer narrower muzzles
ears pretty mcuh any set and mix of sets
longer legs
lighter build
less hair
come in smooth coats


Aussie:
no tail
short blunt muzzles
ears flopped with a slight rise at the base
shorter legs
heavily boned
always longish thick hair

example:

red merle Border collie(Happys sire)


red merle aussie