The little scope on the QB78 is a cheap little 6X (
http://www.cdnninvestments.com/tasp6xulcosc.html )...think I spent all of $19 on it (you'll have to do the conversion)....liked it so much, ordered two more for other CO2 guns. Honestly, think the same scope in 4X is a better option....and don't know if CDNN ships out of the US or not. Did readjust the objective to be parallax free at 25yards, which I find useful for hunting shots from 20 to 40yards.
The big scope on the AR2078 is another inexpensive one (
http://www.cdnninvestments.com/tasp10tap4re.html ). This one is a 10X and a 30mm tube, but it seems to work out pretty well on that rifle.
I'm not opposed to expensive scopes...but haven't found anything to complain about with these inexpensive ones. Generally best to keep a cheap-scope as simple as possible...the fewer bells and whistles the better...which is why both of those scopes are fixed power, non lighted reticle, and "basic".