had a 2018 Sierra All Terrain 5.3 with the Trifecta tune
and now a 2021 6.2 Trailboss (waiting on range DFM disabler, dont want a pulsar)
after the tune on the 5.3 it also recommended premium, 6.2 will run on 87 but the fuel ecoomy on premium pretty much offsets the extra cost on the 6.2 , pay more, go futher on a tank. works out to a couple bucks a tank even on overpriced Canadian gas here in Ontario once you consider the better mileage. and for a few bucks difference, sure you wont notice the slight power loss but id rather not drive my truck around relying on knock sensors to constantly pull timing
found the bigger wheels and rims were noticable on the 5.3 where the 6.2 i couldnt tell any difference, certainly more passing power on the 6.2, i dont tow often just put alot of crap in the truck and box for hunting, fishing and cottage trips and a few trips across farm fields to setup treestands etc
went 6.2 this time around just because the likes of the ecoboost and ram, and now the Tundra all make alot more HP/TQ than the 5.3, 5.3 just felt sluggish after driving those
end of the day buy what you want, i traded my '18 in for a ct5v and it was fast and fun, hard to go back to the 5.3 after that but i missed my truck, although the 5.3 would do everything i needed and more.. i just wanted the power, no need to justify it, if ya want it get it... if ya wana save a few bucks then get the 5.3
not sure i could do the 2.7 yet, just dont like turbo gas engines in a truck and those 4 bangers must be strung out to make that kind of torque, crazy power from 2.7 no doubt, would say itll be interesting to see how they are doing in 5 years, i see the 2022 they beefed up the block, but the MPG on them isnt any better than the 5.3