Bont+Lycett vs Fyfe+O’Brien
Not an option you listed, but Bont and O'Brien for me out of those.
O'Brien I don't see dropping off significantly and the year of experience should help if anything. If there weren't two dominant rucks, I'd definitely consider him. Lycett I'm not super bullish on, he's capable as I mentioned in my last post, but I definitely prefer O'Brien of the two.
Bont has just turned 24 and is coming off 5 straight 100+ seasons, Fyfe 28 with 7 straight 100+ (3 of them 120+). Fyfe has arguably shown a higher ceiling and has less competition in the team for points, he's probably a bit less durable never playing all 22 matches (Bont has in 3/6 seasons). Either are good selections, I just think Bont is possibly on the improve, Fyfe is at his peak.