I do this route a fair bit and have always been Platinum when doing it, also I have always been on reward seats.
From Y I have a 50% upgrade record (always only to PE) which is pretty good.
If stuck in Y, I always take row 20 window, mainly because I find it easy to sleep putting my legs up against the wall in front. Just take some ear plugs because I am yet to be on a flight with no babies in that row.
Other than that, as a Plat only other benefits on this route have been special service of food (get first choice and brought out to you before main service, along with people getting special meals) express cards have been hit and miss when in Y but also get them when in PE.
For what its worth, if your Plat and you get a decent seat in Y its very hard to justify the extra cost of PE on this route. The food is marginally better but still served in the same coughpy containers with the foil and cling film on.
Another tip on this route, if you get hungry easy, take snacks! you will get a meal about an hour in, then a snack (small sandwhich or similar) about 5 hours after that then breakfast about an hour before landing, I just can't go 5 hours with no food. In Y the only snacks are plain chips and soft drink.
They used to let you pick the exit for free at checkin and now they don't (well not last time I tried anyway, but that was leaving LAX)