Being able to accept money when someone tries to pay you is very important!  When an individual sale can result in money like this you want to make completely sure you are able to accept payments when someone wants to give it to you!

Paypal is a very well known and trusted merchant, it has the advantage of instantly being able to withdraw your money but the commissions can be quite high in comparison to other merchant accounts.

SWREG is more competitive on the commissions side but you have to wait as they only pay out monthly.

I personally use both, you should have as many options available as possible for your customers to give you their money.