There is not much difference between routing using resolve and not using it.
The only main difference between these two are:
No Resolving:
After changing the browser URL it jumps to route first and then get data later.
Using Resolving:
After changing the browser URL it get the data first and then jumps to route(and pass data).
You can also check out the link of General workflow of routing with no resolve and workflow of routing with resolve.