Both give you your real situation in Switzerland — taxes, health insurance, rent, commuting — before you arrive. Only one includes the search for a municipality.
Installation
You already have a home. What you will have left each month, and what settling in will cost.
Relocation
You are looking for where to live. Everything in Installation, plus ten recommended municipalities with their disposable income.
Not sure? If you have not signed a lease yet, take Relocation: that is where your budget is decided.
What to know before you order.