Angular Http - toPromise or subscribe

I think as long as the response is not a data stream that you're going to use, then you'd better use the .toPromise() approach, because it's meaningless to keep listening to a response that you don't need and it's not even going to change.

UPDATE

.toPromise() is now deprecated in RxJS 7, they replaced it with something better firstValueFrom and lastValueFrom.

So your code should look like this:
await lastValueFrom(httpRequest$)

For more info about this check these links:
https://rxjs.dev/deprecations/to-promise
https://www.youtube.com/watch?v=3aeK5SfWBSU

If you like the reactive programming style and want to be consistent within your application to always use observables even for single events (instead of streams of events) then use observables. If that doesn't matter to you, then use toPromise().

One advantage of observables is, that you can cancel the request.

See also Angular - Promise vs Observable