Quick pros and cons, I might be forgetting some.
MST Pros:
- IEEE standard
- scales well in terms of number of vlans handled (only one bpdu sent per physical link, efficient in term of CPU utilization).
MST cons:
- need to maintain the MST configuration identical on all switches in order to keep them into a single region.
- topology changes advertised with the granularity of the instance (not the vlan). This will be fixed when MVRP is available.
- interaction with PVST is not obvious and honestly not recommended if you can avoid it.
Rapid-PVST pros:
- Obvious migration from PVST.
- No MST configuration to handle.
- Provides the convergence speed of MST in most cases.
Rapid-PVST cons:
- one STP instance is ran per vlan (not scalable).
- proprietary. Interaction with third party bridges is not as obvious as what most engineers think (not all topologies can be achieved for vlans != 1 for example).
- Probably not as future-proof as MST (new features are rather developed with MST in mind).
Regasds,
Francois