Yongnuo YN-560II vs Sunpak PZ42X

I am buying my first flash for a Canon 40D (on a v.tight budget) and have been going round and round in circles. I have ended up at the Sunpak or the Yongnuo but they are not quite equally matched. The Sunpak is TTL and claims to work with the Canon E-TTL but has no slave function. and the Yongnuo has a slave function but is manual only. This is my first true flash and it is to learn with. Has anybody any advice........other than buy a Canon Speedlite!