Taps and Mixers - What's the difference?
Taps and Mixers appear to be doing the same thing: They control how much water flows from the outlet and at what temperature. But while that might be all one notices when washing hands, the mechanics inside the wall differ greatly - and offer opportunities!
Mixers
Mixers do exactly what their name suggests. They mix cold and hot water to produce a single flow of water at the correct temperature. This requires the use a carefully designed ceramic cartridge that allows controlling both the mixture and the overall flow. While this might sound complicated, in actual use, these ceramic cartridges are extremely reliable and long lasting. Mixers are available in lever designs and as turning knobs, so called progressive cartridge mixers.
Lever Mixers
Lever mixers use the three dimensional movement of the lever to control flow and temperature at once. Up and down usually control flow rate, with left and right adjusting the mix of hot and cold water to reach the desired temperature. The Vivid Slimline range by Phoenix and the Yokato range by Brodware feature examples of this style.
Progressive Mixers
Progressive Mixers only turn on one axis, and so must control flow and temperature differently. In the case of the Phoenix Toi and Ortho ranges, this is done by dividing the turn range of the control knob into different sections. Turning the knob from the off position will at first only increase the cold water flow rate. Once the flow rate reaches its maximum, continuing to turn will change the mixture to include more and more hot water, increasing the temperature.
Taps and Wall Top Assemblies
Unlike mixers, taps, or wall top assemblies as some suppliers call them, use separate controls for the hot and cold water inlets. This allows for the use of simpler to make jumper valves that use no ceramics, but due to the superior long life quality of ceramic cartridges, many taps still include them even so. The use of taps requires a separate outlet, though. Most suppliers provide matching sets, as with the Phoenix Nostalgia range or the Brodware Winslow and Neu England collections, but most are also available separately to allow you full control and choice over your bathroom look.
Which should I choose?
Mixers will evoke a more modern look, take up less visible space and allow for full control with one hand's touch. Taps meanwhile go well with traditional styles and can offer a stronger presence for your design style. In the end, the choice is yours!