The Rivian is a truck, the F150 is by far the best selling truck, I don't think there could be a better comparison.

What would you compare the Rivian to?

That only works if you take it at face value that buying either of them is a rational transportation choice, which I reject. Even if I accept the people need a weird truck-shaped thing with a useless 4.5-foot bed, a far better choice on emissions grounds would be the Ford Maverick XL, which has a battery 1% as massive as the R1T's battery, yet this tiny battery cuts the per-mile GHG emissions in half. The embodied carbon payback distance of an R1T versus a Maverick XL is over 100,000 miles.

My kid races mountain bikes so I have become extremely familiar with Rivian (and Cybertruck) MTB Dad, and I think they are a joke. With only a little planning I can get three bikes and three riders in a Honda Insight, while R1T Dad needs an optional accessory to get even one bike in the bed. People choosing these things are, 99% of the time, not behaving rationally. They are buying luxury goods that they believe signal their environmental credentials.

I don't find either truck a rational choice, but the car market can stay irrational longer than the climate can stay liquid.

The cultural irrationality of the truck/car market in the US crosses all ethnicities and class lines. If we are trying to evaluate the effectiveness of EVs, I think we need to compare the Rivian to the closest fossil fuel powered vehicle, even if it's something that causes me to disrespect the people making these choices.