If you want to take about resource efficiency, we should probably start by eating what we produce. A quick Google turned up this report that 40% of the food produced in the US is thrown out as waste.
You know, I read that back in college, was properly outraged, resolved to eat all the food I served myself for every meal and never serve myself more than I would eat from then on, have done so ever since, and then proceeded to forget my original reason for doing so? That figure had passed out of my mind until you brought it up just now.
That said, the efficiency gap, while large, is still considerably less than that between raising meat and produce, so a person would actually be wasting fewer resources if they were eating only produce and served themselves...
I notice that a large fraction of Effective Altruism people are vegetarian. This makes sense: in general Effective Altruists take moral issues seriously, even when that means changing your lifestyle. I'm not sure it's a good balance, though.
One way to think about this is to convert it into money. How much would I need to be paid to give up eating meat? All animal products? How much money would I need to spend on myself to be about as happy as I would be with less money but continuing to eat animals? I'd probably be willing to go vegetarian for about $500/year, vegan for maybe $2000/year.
It turns out you can probably pay to convince other people to be vegetarian much more cheaply than that. I estimate the cost of a vegetarian-year at $4.29 to $536 while Brian Tomasik estimates $11 with better methodology (which I looked at). This is by placing ads on facebook for a site where people can watch an animial cruelty video and ideally become vegetarian or vegan.
If you would get more than $11/year worth of enjoyment out of continuing to eat meat, why not give $11/year to convince someone else to not eat meat for you? Or give $50/year and be on the safe side?
(While you're giving money, you should probably give it to the organization that you think will do the most good with it, which I think is probably one of GiveWell's top charities. The nice thing about money as opposed to actions is that it's easy to redirect.)
I also posted this on my blog.