We were studying about nucleophilic substitution reactions. My professor said that in general SN1 reactions are faster than SN2 reactions. I am unable to understand that how can we generalise the rate of two completely different reactions. In this case, what I think is that the rate will depend on our reagent, leaving group, solvent, etc and in some cases SN1 will be faster while in some others SN2. Therefore, I'm a bit confused.
I would be happy if anyone could help me with this.