Some low light scope tests have been made by Finnish hunting magazine Metsästys & Kalastus during the past two years. Here are the links for the results:
The Optics Talk Forums - Finland Low Light Scope Test - Page 1
The Optics Talk Forums - Finnish low light scope test - 50mm scopes
In 2005 Finnish gun magazine Ase-lehti made a pretty thorough tactical scope test containing 15 scopes. Nightforce NXS 5.5-22x50 was on par with Meopta 3000 4-16x44 Tactic in low light performance beating for example IOR Luneta 4-14x50 and 6-24x50 and _clearly_ beating Leupold Mark 4 4.5-14x50. S&B and Zeiss scopes were superb in low light. Low light performance was measured by trying to read boards containing line pairs and also consider if the shooter would be able to make a shot at the target.
Zeiss Diavari 6-24x56 V T LA ret #63
21:05 4. line pair still visible. Able to shoot.
21:35 Both reticle and target still visible. Able to shoot.
Nightforce NXS 5.5-22x50 MLR
21:05 4. line pair visible. Able to shoot.
21:35 Target and reticle somehow visible. Shooting is uncertain.
Leupold mk4 4.5-14x50 LTR M1
19:40 Hard to see line pairs 1 and 2
20:05 Cannot see clearly
20:35 Cannot see any of the line pairs
IMO the performance of Nightforce was very impressive in this test. I wonder why the BR model didn´t cope in the M&K 56mm test. Either the mid-European manufacturers had increased their lead in low light performance or BR has different lenses than NXS. Go figure.
To my knowledge the new VX3 has inhereted features from VX-7 which may boost their low light performance. I haven´t yet seen any low light reviews on either of them. There are rumours saying that Meopta makes the optics for Zeiss Conquests. If the lenses are finished and coated the same way as in Meopta Meostar scopes, they should be pretty good low light performers.