I've just started playing in Southern California snow. It turns out even after our 40 year storm a couple weeks back, the snow really sets up fast. I left the snowshoes in the car and used crampons at Mt. Baldy last weekend.
Contrast that to the Sierra where I grew up playing in the snow. I've broken trail with 36" snowshoes where I could barely lift my knee high enough for the next step. I sort of agree that you might need more than one pair of 'shoes for all-winter use in the Sierra.
Back to MSR- has anyone looked at all the various models? I'm curious whether the hinge pin and binding are similar strength on the full line? If so, for highly consolidated Sierra or So-Cal snow it might be fun to try the MSR Shift. It's aimed at kids from 75 to 125 pounds and measures 7"x19.5". They claim it will fit up to Men's 8 boots, which might mean larger trail runners with some trimming of the front deck. Weight is advertised at 2 lb, 7 oz. per pair.
I just bought a pair for my 7 year old. They look great- I'll have a report after we spend this weekend in Sequoia.