New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  first: true,
  componentName: 'x-first',
  
  toggleComponentName() {
    if (this.first) {
      this.set('first', false);
      this.set('componentName', 'x-second');
    } else {
      this.set('first', true);
      this.set('componentName', 'x-first');
    }
  }
});

templates.application.hbs

{{#let (component this.componentName) as |c|}}
  {{c}}
  
  {{component c}}
{{/let}}

<button {{action this.toggleComponentName}}>toggle</button>

templates.components.x-first.hbs

first

templates.components.x-second.hbs

second

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}