I would use Stripe, just because I trust them way more than PayPal and the conditions are slightly better. There's Stripe Checkout (
https://stripe.com/docs/checkout/tutorial), it's not much more effort than a PayPal button (unless you're using it like a donate button).
Whether it looks professional or not depends on your clientele. If your service is good, whether you're using Stripe or PayPal doesn't matter. I'll need some convincing to put my card details into forms from other providers though.
