The verdict
If you sell software or other digital products to customers around the world and nobody on your team wants to run VAT and sales tax, I'd pick Paddle. If you sell to consumers, run a shop or freelance and want to be paid quickly with links and invoices, I'd pick PayPal.
For a software business that will scale, I would not use PayPal as the only payment layer. The fee depends on country, method and volume, and you get less control over billing. For a small shop, Paddle is more than you need. Check the Paddle account review and custom quote rules before you build on it, especially if your products are low-priced.