DC Resistance is often misunderstood, and is therefore sometimes used erroneously as a means of comparing two pickups.
The conventional wisdom is that a pickup with higher DC resistance will have a higher output, but this is often not the case. DC resistance measurements for pickups are only useful when comparing two pickups that are the same in every other way.
Copper wire, like all materials, resists electrical current flow to some degree. Thinner copper wire has a higher resistance to current flow than thicker copper wire. You can think of this in terms of water hose: a thicker hose allows more water to flow through than a thinner hose.
So a pickup with 7000 turns of 42 gauge wire will have less resistance than a pickup with 7000 turns of 43 gauge wire, since the thinner 43 gauge wire has a higher resistance-per-foot (the higher the gauge number, the thinner the wire). This assumes both bobbins are the same.
DC resistance doesn't correlate to output per se; output is primarily a function of the number of turns of wire and the magnet strength. When comparing two pickups with identical bobbins and identical wire gauge, DC resistance measurements will show which coil has more turns of wire, and -- again, with all other things being equal, including magnets -- which pickup has the greater output.
But there are other factors that murky the water further. The amount of tension that's placed on the wire during the winding process is a factor, in part because 42 gauge copper wire (approximately .004" in diameter) is easily stretched, and stretching wire reduces its diameter and increases its resistance-per-foot.
Also, wire varies from batch to batch. It's formed by drawing it through dies, but there are bound to be deviations in the dies from one manufacturer to another, and dies wear. For these and other reasons, all standardized wire gauge specifications have allowable tolerances (AWG -- American Wire Gauge -- is the spec primarily used in the US).
And temperature also affects resistance. You can see this by clipping meter leads to a pickup, then holding it in your hand. As the coil warms up in your hand, you'll see the DC resistance creep up. This isn't going to make a world of difference, but it is a factor.
And finally, how accurate is your meter? And how accurate is the manufacturer's meter? And how carefully were the readings taken? And was the pickup measured while in the guitar's circuit, or isolated from the circuit?
There are many variables, and so pickup manufacturers dislike DC resistance numbers, because they're taken as gospel by many customers who become dissatisfied if their pickup doesn't "measure up". Pickup makers publish these numbers because the public demand it, but they understand there will be deviations from a stated spec, and they don't want to have their feet held to the fire if a particular pickup deviates modestly from the number that they've published. They are much more interested in turn counts than they are in DC resistance measurements.