If price and weight is no object then you can get any saw you want. There is no need to even ask.
If it is, then you have to figure out what you need, vs having the biggest saw in the neighborhood.
If you do have price and or weight constraints, then you have to weigh the factors and decide.
What I can say for sure is you can push a Stihl saw that's too small way over the limit, as long as you don't do it a lot. If you need extra reach and go pup 20% of the time, then you don't need the maximum size saw that can handle it, you buy the saw that does the 80% job, and work it harder for that 20%
At some point, the balance is tipped, not purely on percentages, but on effort and annoyance and time. At 30% it may be costing you more time and effort than you can afford or want to spend, and then you go with the bigger saw (assuming you can afford it)
Bigger saws usually mean more weight (though the transition between the older MS390 and the new MS361 means the there is a 7/10 Pound weight different, as they got more power out of the newer design). You also pay $130 more. Thats not a lot, but if you don't use it, its a waste.
In the case of the 460 vs the 660 you are carryng 2 pounds more weight, and around and $200 more, not to mention the dynamics of use. Do you really need one more hp for that? Do you need that extra 4 inche on the bar?
Only if the mission requires it. Otherwise the 460 is fine, and you can work the 460 harder occasionally if the need is rare.
Reality is that neither of those saws is going to get worn out by an occasional user.
The so called Mid range saws will probably wind up obsolete before they get worn out.
Pr use is going to wear out any of those saws, that's why they rebuild them or buy a new one and usually they have a good spare on hand, as that's how they earn their living).