Normalize the problem before comparing
Ask every alternative to address the same workloads, growth, dependencies, availability and migration constraints.
- Included services and environments.
- Capacity and growth assumptions.
- Activities excluded or owned by the client.
Separate acquisition from operation
The decision should show who manages, monitors, updates, backs up and responds after go-live.
- Implementation and operational responsibilities.
- Support and escalation model.
- Licenses, renewals and recurring services.
Require a transition path
A complete proposal explains validation, go/no-go conditions and how a stage is reversed when results are not acceptable.