I wonder whether is it ok to compare guitar pickup output by resistance measured? Is it possible that both pickup will be 10k but give very different output level?
Measuring the DC resistance of a pickup has become a popular catch-all way of implying a pickup's output. Unfortunately this is only one piece of a puzzle, and should not be used to infer the output of a pickup (or tonal characteristics either). The resistance of the pickup itself isn't very useful if you don't know, for example, the gauge of wire used in the pickup. Fewer turns of thicker wire will have a similar resistance to more turns of a thinner wire. Moreover the magnets used in the pickup can also alter the output. For example some Rickenbacker pickups are quite over-wound, but because they use weak rubberised magnets, and on some pickups erroneously screw the pole-pieces into the core of the magnet rather than simply touching one pole, the pickups are quite weak. Some builders use neodymium magnets in their pickups which, combined with a relatively low number of turns of wire, can produce a surprisingly high output pickup.
A fuller description of the various attributes that contribute to a pickup's output is given here: Pickup DC Resistance and Output Levels.
DC resistance is almost completely irrelevant, other than when considering impedance matching between the pickup and possible active electronics. The output of a pickup is AC, so at the least you'd want to try to measure the inductance over audio frequency ranges.
At the "basic physics" level, every 360 coil generates the same EMF in response to the external moving conductor (the string); these EMFs add linearly to produce the output EMF. As ABragg said, the type and strength of the pole piece strongly affects the coupling to the string in the first place.
Personally, I'd be much more interested in the relative output as a function of frequency than the absolute output level.