I'd call it about even skrill in order for someone to charge you back it has to be through there credit or debit card company. Which makes it a hassle for people because they are required so much information to approve the dispute and still they might not win it without enough proof. Usually scammers do not take the time to go through that process but it has happen to me before with 45$ and they ended up getting the money back but skrill evened my balance.
Now with paypal if you are a business and you are selling virtual items you are 100% covered by protections if you are running a business, I cannot say the same for payments that are sent via gift. If you are selling virtual items if you get a dispute opened on you just call paypal and explain the situation and they will close the case in your favor.
Just read the T.O.S and AUP of both companies and it will give you basically the whole run down of the in and outs but you have to take the time to read it yourself people explaining it to you might mix things up.