A lot depends on whether you mean:

* R0 when the disease appears first time and people dont know about it

* R0 when people learned about disease and changed behavior.

Assuming disease is new, one person sick with SARS will infect more people then one person sick with COVID.

Due to stronger symptoms and shorter time to symptoms, we learn SARS is issue, change our behavior and quickly close small area. SARS will spread less. In covid, by the time we figure area is infected, a lot of people are infected elsewhere. It takes us more time to react.

R0 is what it is, but I agree, it seems like there should be a more meaningful measure that takes factors like incubation period into account.