Which is better? I'm not certain. Here's what I've worked out thus far using a couple hypotheticals. This is based on a few assumptions.
1) According to the wiki the maximum bush camo value is +64%, but actual bush camo values are unknown and highly variable, so I just went for worst-case scenario and hope that's correct.
2) The CVS works the way it says it does on the tin. This is not a given, there was plenty of equipment that didn't actually work the way you thought it would (Vstabs were more effective than labeled, spall liners considerably less).
3) The math is right. Is it ever? This math is premised on the CVS reduction in camo applying to the sum total camo value of tank + bush, and not just the camo value added by the bush alone, or only the camo of the tank behind the bush. If it doesn't behave the way I've got it laid out in the equation the gear will be less effective than shown here.
Note: Any effective view range <50 meters is irrelevant, you'll just proxy spot them at 50 meters…and they'll do the same to you.
If you have to pick one, optics will do slightly better against targets in the open but much worse against bushed up targets. I'm leaning towards CVS if you have to do just one.
If you have both it seems like you want +CVS & optics, being basically equal to +optics & CVS for targets in the open but much better against targets bushed up.
Seems generally similar, optics alone are more effective than CVS alone for targets in the open (say, arty in transit or on maps without much foliage), with the situation reversed with bushes.
CVS seems stronger in its niche than optics in its niche.
Edit: XML information on the CVS. What remains to be seen is whether "demaskFoliageFactor" is applied only to the camo provided by the bush or the sum total of camo in the bush.
<commandersView> <id>100</id> <userString>#artefacts:commandersView/name</userString> <shortDescriptionSpecial>#artefacts:commandersView/short_special</shortDescriptionSpecial> <longDescriptionSpecial>#artefacts:commandersView/long_special</longDescriptionSpecial> <icon>../maps/icons/artefact/commandersView.png 0 0</icon> <price>600000</price> <tags></tags> <categories>stealth</categories> <vehicleFilter> <include> <vehicle> <tags>lightTank mediumTank</tags> <minLevel>8</minLevel> <maxLevel>10</maxLevel> </vehicle> </include> </vehicleFilter> <script>StaticOptionalDevice<weight>100</weight><factors><factor><attribute>miscAttrs/demaskFoliageFactor</attribute><type>mul</type><valueByLevel>0.85 0.8</valueByLevel></factor><factor><attribute>miscAttrs/demaskMovingFactor</attribute><type>mul</type><valueByLevel>0.9 0.875</valueByLevel></factor></factors></script> <kpi> <mul> <name>demaskFoliageFactor</name> <value>0.85</value> <specValue>0.80</specValue> </mul> <mul> <name>demaskMovingFactor</name> <value>0.9</value> <specValue>0.875</specValue> </mul> </kpi> </commandersView>