Long story short is lack of reliability and instant power.
I had a 2007 Tundra 5.7L and now have a 2018 3.5L TT.
The Tundra was great with its instant power and reliability. For the 12 years I owned it there was one recall and one part failure.
The F150 has been the exact opposite. There has been several recalls and some they call TSB's, FSA's, etc. I think the total of these are around eight so far. It has been in the shop too many times to count: freezing door locks, fire hazard on safety belts, braking system malfunction, door locks not working, Sync 3 not working, cam phaser rattle, complete loss of power when going from 3rd to 4th (have been close to being t-boned twice), cam phaser FSA (which hasn't worked), and a few things I can't remember right now. Thank god I have been working from home the past 1.5 years. With all that, luckily, it has not stranded me yet. Also, while the truck has plenty of power, I do not like to tow with it. It drinks the gas so fast I can't pass a gas station without stopping. If I lock the transmission to only use 7 gears then it is better but not great. Therefore I prefer to tow with the Tundra (son drives it now).
I bought the F150 because I didn't want to buy the same generation Tundra and the inside of the F150 cab is amazing . The fit, comfort, and technology are top notch.