Craft plugin or external application
In my company we work with Craft and Laravel only, so this question comes up quite often and is a moving target as time passes and both platforms evolve.

Since Craft is built on Yii you can do almost everything what you can do with Laravel. You have basically 3 options here: Craft-only, Nova-only or a hybrid. I would ask myself at least the following questions to make a decision:


Do you need to write a lot of tests for the business logic? -> even though Craft caught up on testing, still +1 for Nova and Laravel
Is the editorial part of the application really trivial? Like, can you avoid having complexity in the editorial and business logic part of the application? -> +1 for the hybrid
Do both parts of the application really have to communicate with each other? Can you avoid a shared user authentication? (should generally considered as last option IMO) -> +1 for the hybrid
What about integrations, are there plugins/packages available that you can use right away? -> depends on the research
Is there any show stopper for the business logic part regarding Craft? (Arbitrary example: You need a multi-tenancy architecture, don't take Craft-only.)


So in the end the good news is, there is not necessarily a right or a wrong answer here. The bad news is, either way you go you'll always feel like: "What if I had..."

You see, personally I lean more towards Laravel for custom application development, just because I am more comfortable with it than with Yii. I would definitely consider to take the advantages of both platforms in exchange for a bigger code base and maintenance effort. But only if one application part can be dumb and the other complex.

Maybe now you are even more uncertain than before :)