We could cut down on oxygen use by not breathing too. Ultimately you have to ground these abstract vectors of comparison in some fundamental purpose. For me, the only possible ground is humanity.
If humanity is the ground of your analysis, meat consumption will fail to present itself as the decisive factor for any vector of comparison. The decisive factor will generally be the elevation of capital or oligarchic social ends over general social interest.
It would allow nature to begin to recover from the damage we've been doing to it for thousands of years. Besides increased biodiversity being an inherently good thing, it would also reduce flooding and erosion, stabilise weather systems, preserve topsoil, etc. etc.
I've seen a number of reports of large farms being planned in places like the middle east.
Dubai opened one about 6 months ago capable of producing over a million kg of leafy greens a year, the largest vertical farm in the world by some margin, and that's just a pilot project.
A million kg of the most calorie dense leafy green (parsnip or kale at 50-60 kcal/100 grams) would be equivalent to about 167,000 kg of wheat (~360 kcal/100 grams). A bushel of wheat is about 27kg and the US produces about 50 bushels per acre [1] or 1,350 kg of wheat per acre. To produce the caloric equivalent of a million kg of leafy greens you would need about 130 acres (167,000/1350) of wheat. The average farm in the US is over 400 acres in size [2]. There are over two million farms in the US alone.
The “largest vertical farm in the world by some margin” produces less calories than a tiny family farm that can barely afford its own tractor. The largest wheat farm in Canada is over 35,000 acres which means it produces just as much food per day as the largest vertical farm produces per year. That wheat farm isn’t even in the list of top 10 largest farms in North America.
Edit: I made a slight mistake in my math. A 60 lbs bushel of wheat when processed doesn’t yield exactly 60 pounds of usable food, but it doesn’t change the overall picture (360 kcal => 240 kcal, 130 acres => 180 acres)
Edit 2: That vertical farm cost $40 million to build. Our hypothetical wheat farm would cost under $2 million for the land, fertilizer, seeds, and machines.
There will still be a relation, `more vertical farms => more use of water and pesticides`. Now, the factor between those might change. But I fail to see why vertical farming would change the dynamics fundamentally.