The classification should be in how much work can be performed for the weight of the saw. I don't know, but for the little run time I had on the slightly modified 261 I ran, it was getting into or was into the 361 range (its be a long time since I ran a stock 361, so my gauge is off on that I'm sure), but the 261 for its heavier weight will completely out perform a 260, in power and much less fuel consumption, this is very important, as there are few that need to one hand the 261 all day. I personally find that for all day, sun up to sun down cutting with 30 minutes off for lunch, the weight of a saw isn't a problem until you get into the 90cc range, then weight differences of say 1 pound become more noticeable.
For instance, in the 70-80cc range you have lighter 440/372's and heavier 460/576AT's and some in the middle of the 1 pound of wieght range, yet it make little difference for all day work, yet many on this site that will complain the loudest about a few ounces are the ones that use the saws the least, LOL.
Indianspring's workers are a fine example of a heavier but more efficient 261 being the saw of choice for all day cutting of firewood in a professional setting, the 346 is lighter ...... and still nobody wants to run it, and his workers that don't have an axe to grind (Stihl vs Husky), they just need a tool that gets the job done, naturally a good worker will gravitate toward the tool that most assists a guy/gal in getting that work done quickly, efficiently and comfortably.
I have found that the choice of a saw in the difference CC brackets is best chosen based on the potential work that can be performed within a synergistic design or grouping of parts, and not so much dependant on a couple of seconds faster in the cookie cutting times or being lighter or heavier by a few ounces or sideways balance or other such statistics that make a good showing in writing or on charts or short videos, but don't quite add up enough to offset other detriments or holes in the efficiency bracket when it comes to real world cutting.
Sam