A dimmable LED has two features, one is it has a leak resistor so a small amount of power can flow without causing the LED to come on dim or flash, and two it either has a very simple current control or a pulse width modulated control able to read the leading or lagging phase clipping of the dimmer unit. With large 10W or more units the percentage loss to make them dimmable is not worth worrying about, but with multi small units i.e. 10 x 3W LED candle bulbs the losses mount up, and instead of 100 lumens per watt they drop to 60 lumen per watt.
In general LED lamps leak around ½ watt to work the dimmer.
The older dimmers needed a lot more than ½ watt to work the dimmer, although using 10 lamps may mean you get 5W wastage which is enough to get the dimmer to work, one has to ask do you want to use such an inefficient dimmer?
Even simple switches waste a small amount of power because of the way they are traditionally wired, the line and neutral should follow each other around the circuit to keep the balance between capacitance and inductance, but we take the line only to the switch, which did not cause a problem with the old tungsten system, but specially with two way can cause problems with the very low current used with a LED.
So buy a 3W LED and around 60 lumen per watt and a 24 watt LED (fluorescent tube replacement) and around the 100 lumen per watt as all lamps regardless of size need to leak the same amount of current to over come the wiring not being balanced.
The only way around the problem is to use DC only LED packages. But most even 12 volt are designed to run on AC odd they often don't say AC, but say 50 Hz.
Because when a LED is dimmed the colour does not change, not sure there is any point in dimming a LED lamp, Switching on more or less lamps is a better idea. Two exceptions, one children's bed rooms where you don't want to wake child, and public places where you want the public to realise the lights are about to go out before being plunged into darkness as in a cinema.
Although I may buy dimmable LED lamps because they are cheap, I will also buy non dimmable LED lamps because they are more economical, so I don't want to fit any dimmer switches.