I've got both the 24" bull bbl'd LR-308 and the 16" AP4. As soon as I get the time to make the switch (kids are freetime leaches):
The 24" rifle is going to be topped with good old (Japanese made) Tasco 6-24x44 target/varmit scope. The quality of the older, Japanese made, Tascos is much better than the newer ones made in China.
The 16" carbine is going to be topped with a 4-12x56mm, illuminated reticle, NcStar that has worked real well on the LR-308. Quality with NcStar seems to be "hit or miss", but this one performs real well as long as you don't go past 10x.
I personally wouldn't choose a 10x scope for a carbine, and will probably end up with a holo sight (the EoTech clone made by Bushnell) on my AP4, but in the meantime my tired old eyes will shoot the scope better than iron sights.
A good, used 3-9x40mm Leupold VX-III can usually be bought off ebay for under $300 if you are patient. IIRC you only get all lens surfaces "MULTI-coated in the VX-III and higher model scopes.