Drinking water and grey water

If somebody could advise please. Our initial foray into caravanning utilised the use of a bucket for grey water and small on-board container under the sink for fresh water. We are now moving up to a bigger van  one with a loo and we have been advised o look at an Aquaroll and a Wastemaster. They  both seem rather large items do we really need them or can we get away with basic plastic containers for both purposes? We really don't know what to do. 

Any help or advice appreciated.

John