A Saxony carpet usually a deep pile and soft, great for any room but will flatten quicker in high traffic areas like a walkthrough or stairs and landings.
Twist pile carpets have 2 yarns twisted together, this makes the carpet able to withstand traffic for a lot longer, not often as soft as Saxony but a great choice for long lasting.
Loop piles are the hardest wearing; the loops flatten and fill the remaining areas to mask the flattening look. In mand made fibres these carpets are extremely cost efficient, durable and great for fitting out large areas.
Man made materials like polyester and polypropelene are dyed 100% through the fibre, this makes it a great choice due to cleanability, you can often bleach clean the carpets removing all manner of stains. You can get these fibres in almost any colour scheme.
Wool or wool blends are much tougher, what they lack in cleanability they gain in lasting quality. A wool carpet with correct care will still look almost new in several years. Moth treated as a standard now for peace of mind.
When thinking about your perfect carpet consider which underlay to place beneath. A jack of all trades foam is cost efficient, while a thin rubber is best suited to underfloor heating, or maybe you need more sound dampening from the sound travelling to the next floor.