The measured difference is 0.6 years in this UK dataset.
MeasureBorder CollieAustralian Shepherd
UK median survival13.1 years13.7 years
95% confidence interval13–13.2 years12.8–14.6 years
Source records20,886286
Descriptive result
Australian Shepherd has the higher point estimate in this source table. That does not prove that one individual animal will live longer, remain healthier or cost less than another.
Survival is not the same as healthspan.
The source comparison does not measure mobility, cognition, independence, lifetime veterinary cost or the effect of a supplement. Differences can reflect population composition, health, care and other confounding.