Deciding on which wattage you require is all down to what kind of application you are fitting the LED tape in.
12w RGB + dual-white LEDs are ideal to be used as feature lighting. Lighting to highlight areas, as a secondary lighting. Ideal for covings, drop down ceilings signage etc. to give a smooth halo effect. The 10w would be preferred to the 5w for these applications if there is a high amount of ambient lighting.
24w RGB + dual-white LEDs are ideal to be used as general lighting or as feature lighting for areas larger than covings etc. For example washing down front bars / back bars / under kitchen cabinet lighting as ‘working light’
For more information, see our support page discussing how bright your LED tape needs to be.