It really comes down to experience and whether you can 'tell the difference' between track lengths.
My old boss(sledder for 30+yrs and owner of a Doo shop) couldn't tell the difference in gearing, clutching, sled set-up, track length, etc. He just rode.
I, on the other hand, can tell very minute differences and track length is definitely noticeable for me. So much so that I've shortened both of my current rides from 162's to 150 and 156.(Rev800 and M-Series Cutler 1000) and never wish I had a longer sled.
My friends and I are constantly pushing each other to get thru the trees faster and faster. Sure stopping, assessing, and sneaking around is part of the boondocking game, but the shorter the sled, the harder it is to get momentum and for our group, that's the level we are at right now.
Now take my dad(World Champion Oval Racer) who's been riding the mountains for 40+yrs is a little older than he likes to admit. His skill level is slowly declining year by year as he simply can't muscle a sled around like he used to. Altho he will deny this, I've noticed a growing distance in our skill levels. And by saying that, I mean, there are certain lines he used to be able to nail, and now he finds himself stuck and upside down in a tree. He's all of 5'4" and 150lbs and has never wanted to ride anything longer than a 151"(153-4-5 now) but he seems to be more at home on a 162 nowadays. Simply because he can start and stop and not get into trouble with no momentum. I bug him all the time that it's a crutch to his riding style now.(He hates that)
I do have a Vector Turbo with a 162(bought used) and my plan for that sled is going to have a 156 sticker under it when all is said and done(different chassis altogether)
I have fun on the 162, but not as much as when I'm on the CPC 156 or my 150 Rev.
If I was to buy a current 4s, no matter the mods, I would stick a 156x3 under it as one of the first mods I did. But that's just me.