M.M.
Hi N.,
I can only tell you my experience with the Graco, as we had the SnugRide carseat. I loved this product. I found it very easy to use and after the first few weeks of recovery I had no trouble carrying it around. I can't comment on the Maxi-Cosi or if it makes a big difference in lightness though. As a side note, any carseat is going to become heavy as the baby grows. When my daughter approached the weight limit and was ready to transition to a toddler seat, it was much harder to tote her weight around - but again, that was her weight + the carseat that made it difficult, not the carseat itself.
Good luck!
MC