I use both, but the QHY5L2 always sees more stars than the QHY5, even though the field of view is smaller - the QHY5L2 is more than twice as sensitive. The QHY5L2 has small pixels and will sense smaller movement - it is the best choice for short fl guidescopes (I use mine with a 180mm and successfully guide an imaging system with 0.91 arc sec pixel scale).
If you intend to use an OAG or ONAG with a long focal length scope, something with bigger pixels might be a better bet (eg lodestar)
http://www.iceinspace.com.au/forum/s...d.php?t=119075 might be worth a look?