First I don't know the state of the implementation of obfsproxy so if they say it is still no ready for use then this is probably the case. That said, using a VPN may hide that you are connecting to IP addresses associated with Tor, but it does not hide the fact that you are using an anonymity service. Furthermore, obfsproxy applies steganography of a sort to disguise the size of packets, Tor packets being very identifiable even if they are not being sent to known Tor node IP addresses. A VPN does not do this.