the 2.7 is supposed to the be most reliable, currently. the 3.5 has had cam phaser issues, if they have that fixed its a great engine. It remains to be seen if they have actually fixed that problem all the way. the new 5.0 some say burns oil. the pre 2018 5.0's where probably the most reliable of all the recent engines.
2015 to 2018 5.0 were pre direct inject and lower compression. Very good engines except for the water pump. It was guaranteed to go out about 90-100k miles and not gently.
Pre 2015 the 5.4 was bad about phaser problems
