I assume there are more options/better prices in El Calafate, but does anyone know if it´s that much of a difference? Thanks.

i suspect the difference is considerable

i have not been to el calafate for 7 years, but i was in el chalten 2 years ago - those areas are growing so fast, that my experience may be somewhat out of date - in '08, the el chalten markets were adequate to supply me for a 10-day backpack trip, but i had to be a bit creative - i believe that el calafate has a proper supermarket (la anonoma?), but i suspect certain items (produce?) are still a bit hard to find

in terms of price, i suspect the difference is not enormous, but i believe that, in terms of selection, the difference is significant - on the other hand, both towns are way better than just about anything one might find along the carretera austral (chile) - and el chalten still has a very nice selection of restaurants & panaderias - anyway, good luck...

To answer my own questions: Not much of a reason to do any pre shopping other than stuff you can´t get in SA anyway, like gu, etc.

If I remember correctly... El Calafate had the slighty better selection. I visited small grocery stores in each place, just under two years ago.

One thing though- few stores seem to have an abundance of plastic grocery bags. I always bring extra (for waste, wet clothes/socks, food, etc) when I travel in the mountains. When I asked in Patagonia I was denied, sometimes rudely... At times, I walked out of the store bear hugging all of my recent purchases- as I had no bag on me whatsoever. So, make sure to bring enough stuff sacks!

Have fun down there! Wish I could go back so bad.....