Which is better - Progressive Web Apps (PWA) or Native Apps?

Here's my 2 cents on PWAs.

PROs:

• Looks and feels like an actual app.
• Affordable as you only need a web developer to build it
  
• Very easy to set up + Cross-platform compatible (since it is web-based)
• Can be integrated into native apps (using a webview) later on
• No installation needed (just save to homescreen).

CONs:

• No push notifications (using WhatsApp push is a good idea, but you are limited to templated messages)
  
• Can't access certain native app capabilities / APIs
• Can be complicated for users to understand (save to homescreen). You will need to create a popup/prompt to educate them on how to do it. For Android, it requires Chrome (may not work with certain browsers that come built-in with the phone)
• Does not save cookies long term (for iOS)

I would say PWAs are great for most online services/tools, and great for light usage. 

If you're on a budget, I'd recommend making a PWA (mobile website + save to homescreen feature).

This currently works for both iOS and Android, and is a great alternative to native apps. In fact, some PWAs are so good these days you can hardly tell the difference (example: this dessert store - try saving the page to your homescreen)

And yes, integrating with WhatsApp is a good move, if you can get it set up. Check out Twilio or Vonage for WhatsApp push APIs, they're quite affordable too.

I would say the best part about PWAs would be the fact it is "open", and you do not need to go through the App Store verification process (many new apps get rejected these days).

However the drawback would be the fact you will have to educate your users to SAVE the site to your homescreen, and you will never truly be able to achieve the native-level smoothness (although that seems to be changing as phones get faster)

Oh and another thing - WhatsApp push only lets you send out TEMPLATED MESSAGES, so the variety of your push notifications are limited.