architecture question - using sub routes vs components - ember.js

Question

I am trying to build a UI with left side bar having filters and right side having actual filtered data.
For loading data into the dynamic part of the UI(right side), which approach is considered better in terms of code quality and app performance ?
Use sub routes (for dynamic part of the UI)
Use separate components that load their own data (for dynamic part of
the UI)

Answer 1

There is not a direct correct answer for that; you can use both ways but here is a few things to consider and in the end I generally prefer to use sub-routes due to the following:
Waiting for UI to load: In case you are using separate components to load their own data; then you need to handle the loading state of the components. What I mean is; if you simply use sub-routes; then model hooks (model, beforeModel, etc.) will wait for the promises to be solved before displaying the data. If you simply provide a loading template (see the guide for details) it will be displayed by default. In case you use components, you might need to deal with displaying an overlay/spinner to give a better UX.
Error Handling: Similarly like loading state management; Ember has already built in support for error handling during route hook methods. You will need to deal with that on your own if you prefer components to make the remote calls. (See guide for details)
Application State: Ember is SPA framework; it is common practice to synchronize application state with the URL. If you use sub-routes; you can simply make use of the query parameters (see the guide for details) and you will be able to share the URL with others and the application will load with the same state. It is a little bit trickier to do the same with components; you still need to use query parameters within the routes and pass the parameters to the components to do that.
Use of component hook methods: If you intend to use the components then you will most likely need to use component hook methods to open the application with default filter values. This means you will need to make some remote call to the server within one or more of init, willRender, didReceiveAttrs component hook methods. I personally do not like remote calling within those methods; because I feel like this should better be done within routes and data should be passed to the components; but this is my personal taste of coding that you should approach the case differently and this is perfectly fine.

Answer 2

Data down, actions up keeps components flexible
In your specific example, I'll propose a third option: separate components that emit actions, have their data loaded by the route's controller, and never manipulate their passed parameters directly in alignment with DDAU.
I would have one component, search-filter searchParams=searchParams onFilterChange=(action 'filterChanged'), for the search filter and another component that is search-results data=searchResults to display the data.
Let's look at the search filter first. Using actions provides you with maximum flexibility since the search filter simply emits some sort of search object on change. Your controller action would look like:
actions: {
filterChanged(searchParams){
this.set('searchParams', searchParams);
//make the search and then update `searchResults`
}
}
which means your search-filter component would aggregate all of the search filter fields into a single search object that's used as the lone parameter of the onFilterChange.
You may think now, "well, why not just do the searching from within the component?" You can, but doing so in a DRY way would mean that on load, you first pass params to the component, a default search is made on didInsertElement which emits a result in an action, which updates the searchResults value. I find this control flow to not be the most obvious. Furthermore, you'd probably need to emit an onSearchError callback, and then potentially other actions / helper options if the act of searching / what search filter params can be applied together ever becomes conditionally dependent on the page in the app.
A component that takes in a search object and emits an action every time a search filter field changes is dead simple to reason about. Since the searchParams are one-way bound, any route that uses this component in it's template can control whether a field field updates (by optionally preventing the updating of searchParams in an invalid case) or whether the search ever fires based of validation rules that may differ between routes. Plus, theres no mocking of dependencies during unit testing.
Think twice before using subroutes
For the subroutes part of your question, I've found deeply nested routes to almost always be an antipattern. By deeply, I mean beyond app->first-child->second child where the first child is a sort of menu like structure that controls the changing between the different displays at the second child level by simple {{link-to}} helpers. If I have to share state between parents and children, I create a first-child-routes-shared-state service rather than doing the modelFor or controllerFor song and dance.
You must also consider when debating using children route vs handlebars {{if}} {{else}} sections whether the back button behavior should return to the previous step or return to the route before you entered the whole section. In a Wire transfer wizard that goes from create -> review -> complete, should I really be able to press the back button from complete to review after already having made the payment?
In the searchFilter + displayData case, they're always in the same route for me. If the search values need to be persistent on URL refresh, I opt for query params.
Lastly, note well that just because /users/:id/profile implies nesting, you can also just use this.route('user-profile', { 'path' : 'users/:id/profile' }) and avoid the nesting altogether.