What brand of tupperware-style (kitchen storage containers) are the easiest to clean?
Glass containers will be the best one to use for liquid and or dry goods that can stain (some spices...)

Either mason jar type of containers or jars with clamp lids; both type can have replaceable lids or seals.

The upside of glass is that it is inert and will clean up easily.
The downside of glass is that they break more easily than plastic.

Plastic containers are good for dry goods (rice, grains, pastas...); they wear down in the long run, but good quality ones will be good for years if taking good care of them.

The downside of plastic is that it can take up odor of what it contains and can stain easily (depending on the plastic quality).
The upside is that they are cheap, and will not break that easily.