I don't know—do you get what you pay for?
I tried VPN Unlimited, and discovered that the VPN portals were often down. I was never able to get consistent and reliable connections, and when I did, it was slow.
I found a Hotspot Shield "pay once for life" deal a while back on StackSocial, so I bought that, and the quality difference is night and day. So far, Hotspot Shield has been fast and reliable.
There's definitely a huge difference in different services. Offering a VPN service is easy in theory but difficult in practice, as I discovered when I tried to set up one of my own servers as a personal VPN server.