You can find routers ranging from tiny 100 watt versions, up to massive 2600 wattheavy duty models so the choice is wide open. If a deep cut is required you can still make several passes with a lower powered tool.
Having settled on a particular power, the operator has to work within that envelope, but can control how the power is delivered by varying the size of the cut, the feed speed and of course by using only very sharp cutters.
Collet capacity is another useful indicator of a router’s capabilities. The most universal sizes are 1/4” and 1/2”, though 6mm, 8mm, 3/8” and 12mm are also available.
Only heavy duty routers are designed to take the 3/8”, 12mm and 1/2” shank cutters, the lighter duty models being restricted to 1/4” or 8mm. There is of course no problem fitting a smaller collet into a heavy duty router, but you cannot fit a bigger collet into a small router.
It would perhaps be useful to break this huge range of power down into distinct classifications and give an indication as to uses within the group.
The diameter of the cutter shank determines how strong it will be. A large diameter cutter mounted on a thin shank will be weaker and more susceptible to higher flexing and bending stresses.