It is not. There are fee differences between sending an invoice and using paypal.me. Paypal invoice charges 2.9% the total cost, paypal.me is flat USD $.30 per exchange. It's not really recommended to use paypal.me for business. Neither would you want to be 100% anonymous if this is going to be your profession. Privacy is very important but building a good, trustworthy relationship with your clients is crucial for success (however, if you're just doing this as a pasttime, you can disregard this note)!
Plus, if you use an invoice, you can attach more information regarding contracts and TOS to each of your payment requests. And it's very useful for the client.