So, I went ahead and bought SotC from PSN and tried this. Over-the-internet-connection (local LAN through a Wireless N router) is horrible, very unstable and with bad lag on high IQ settings, plus for reason my Ps3 glitches and refused to connect to the PSN after a few minutes. It requires a system reset to fix. Is stable and playable on low image quality setting, but then the IQ is garbage (looks like a badly compressed 240p YouTube video).
As for Direct connection, it is indeed much better. Is not perfect, lag is noticeable, has frequent frame-drops and vertical screen tearing and compresion artifacs are noticeable even on the high (+1) IQ setting. But a game that doesn't relies much on good framerate like SotC doesn't suffer at all, I killed 2 colossus and was very enjoyable, but it still is far form how I imagine a native vita port of SotC would look and perform though. But, the main problem I have with this mode is that the range is very limited, too limited to be usable from a room other than the very same one the Ps3 is set up at.
Based on comments here I was expecting Gakai-like permanence through my local WLAN, but sadly is noticeable worse than that. However, direct connection is actually decent. Too bad the range is so limited. :/