5.3 to 3.0 but worried about the oil leaks

[Jricharc]

So I have 19' 5.3 RST w/ 28k miles and I have been looking at ordering a 23' RST 2/ the 3.0. I just saw a 2020 RST exact same color as mine w/ the 3.0 but it has 42k miles, I have heard people having issues with the rear main seals leaking, my brother-in-law has a sierra 3.0 that has a small oil leak somewhere so I am hesitant now on these engines. Are they reliable and that much better than the 5.3? I have a travel trailer that is about 4,500lbs that I pull so I thought the 3.0 might be a better option for fuel economy but curious to hear real world experiences.