We have to distinguish between the three lineups - Homeowner, Farmer and Professional grade saws.
The Homeowner saws are bulky in comparison, but a little space between the engine and vital plastic parts helps prevent meltdowns...
The Farmer variety is similar and definitely bulkier than an equally powered Professional saw.
My personal favorite will always be the 034 AV Super - even next to a 026/MS260 it does not look big or "bulky" in comparison and is surprisingly light for a 61 cc saw with a not too long bar.
Some of the "bulkyness" also derives from the too long bars that most Homeowner grade saws are sold with. If you want light, sleek and slender, you need to go Pro.
Regarding the life time of saws, I don't think that any of the newer saws will make it even half as long as their ancestors - that would be bad for business and manufacturers can no longer afford making good products for varrious reasons...