I have both. 2018 Platinum Tundra and 2020 4R Pro. Previously have had 2010 and 2001 Tundras, and 2001 and 1997 Tacoma’s.
I’ll describe the different characteristics I see with driving them both....
Tundra has a massive interior with crewmax, and is a more comfortable long distance driver. Motor and transmission work very well together. Average 15mpg mixed driving on 33” tires. LED headlights put out crazy good light. The factory premium JBL stereo was laughably bad.
4R has good interior room, but certainly feels small compared to the Tundra. Average 17mpg mixed. Much better in snow / ice driving, in both 2WD and 4WD. Definitely notice the motor having 100 less HP and one less gear. Love how much room the rear cargo area has. Is easier to park due to size, but feel the turning radius is smaller. Head lights are horrible.
You can’t go wrong with either, and almost solely depends on if you need the covered / higher rear cargo area of the 4R more than a pick up bed. We needed the rear cargo area for the dog, and it’s been great. If we go anywhere as a family, without the dog, we take the Tundra.
Have you looked at Sequoias? To be honest, I kind of wish I would have bought the wife a Sequoia (softer ride, more room, and has auto 4x4).