Definitely Webmoney. Skrill is a reversible payment method and they often lock accounts concerning Bitcointrading.
WM is not the best payment method, better take a closer look to PM and Payeer, but they're at least not returning funds back as they like.
Is any of these providers safe against credit card chargeback? Otherwise everyone could be scammed when the scammer used carding to fund the account or charges back his credit card payment.
On the other hand it would be interesting for normal users paying with it and getting scammed by not receiveing what they paid for. So Skrill, Paypal and WM would be good because the scammed buyer could charge back but PM and Payeer would be a lost cause?