I'm no dietitian but how much nutrition there actually is per 1kg of beef compared to 1kg of potatoes/pumpkin/onions, etc.?

My sister is vegan, and whenever we have a vegan meal, I'm already hungry 2 hours after the meal. On the other hand, if I eat a burger for lunch, I might not be even hungry by dinner time. Again, I'm not a dietitian so I'm pretty ignorant about these things, but if it has to do with proteins, I think the ROI for meat proteins is going to be a lot higher compared to vegetables.

I realize this gets complicated, but just another counter argument for ROI of meat compared to vegetables.