Both ink and toner are an important part of printing and without either the printing process would be rendered useless. However, there is a common misconception among people that ink and toner is the same thing, but this is not so, they are actually very different.
When you discuss the similarities between the two different cartridges you will realise that they are similar only in structure and composition and also in the way they are used. There are very few differences in the basic design and structure of each cartridge, there are only a few minor differences in the design that would allow you to tell them apart.
In general two different cartridges are placed in the printer, one of these cartridges is coloured, containing three primary colours. The other cartridge contains only black ink. Toner cartridges also work in the same way, with also the same colour parameters. However the design similarities end here, with toner cartridges containing a powder like material simply called 'toner'. Regardless of the fact that toner is dry and ink is wet they are both printed on to the paper through the print head and they both serve the same purpose. They are also both considered environmentally friendly.
It is their name that aptly describes their difference, Ink cartridges and toner; the former is used in ink jet printers while the later is used in laser printers. Understanding this, one would see that despite the structural similarities between both cartridges it is not possible to interchange, that is, use ink jet cartridges in laser printers and vice versa. If a printer has not been designed for a certain type of ink it simply will not be able to make use of it.
Also, for the more fiscally responsible consumer, both toner and ink cartridges can be refilled, rather than having to buy a whole new cartridge.
If you are choosing which to buy it depends largely on what you want. If you are looking to save money laser printers and toner are quite costly, but if you want high quality and high printing output then laser printers would be more down your alley. If you are looking for a printer for your own household then ink printers would suit you better.
Generally speaking ink printers are compact and less expensive than laser printers. Ink cartridges are also available for many different purposes, making them very usefully, whether for photographic work or numerous other projects. But dissimilar to laser toner printers, they are slower and are of worse quality. This quality difference is due to the pigment ink used in ink jet printers being more water and light resistant, while the dry dye based ink found in laser toner printers is much better at projecting colour and indeed holding it. As you can see, it is the differences between the cartridges that will ultimately play a large role in your choice of cartridge and printer. Neither cartridge is better overall, it is merely a consideration of your needs.