Snail mail is delivered by guys in trucks / jeeps - sometimes on foot, still lots of fuel to carry around all that glossy printed (mostly uneconomical to recycle) paper. Per unit-information carried, snail mail has enormously higher environmental impact.

Now, if you feel special enough to think you have your own personal LLM agents targeting you with web advertising... maybe that's costing the same as your share of sending the mail truck around to you - but I don't think the internet marketers are quite there with burning the tokens just to try to hit you, personally, with offers you can't refuse. Mostly you're just a statistic in the bigger algorithms that fill your feed from troughs A, R and X.