Cable insulation is a very important factor for motors. Cable insulation prevents cable short circuits in two ways:

1. Abrasion resistance: Better abrasion resistance reduces the likelihood of short-circuiting when winding a motor. If your motor has debris in the stator insulation or tends to rub on the wires when winding, it could mean the difference between failure and success.

2. Heat resistance: the more heat the cable can withstand, the hotter the motor can run without burning out. I've seen motors burn out (i.e., open-circuit burn out) parallel wires and continue to run under high-temperature insulation. Of course, hot wire can be difficult to solder. It's often considered "unsolderable", which means you have to burn/scratch/sand the insulation before soldering.

Double Coated Wire
In some cases, cables may have a double layer of insulation. The outer coating is usually a smooth, abrasion-resistant coating such as polyamide (also known as nylon) to aid rolling. The inner lining is usually a heat-resistant lining. Sometimes coatings are also mixed for chemical resistance.

Common Insulation Types
Enamel (Formvar): Low temperature (105 degrees Celsius - Class A) and poor abrasion resistance, average chemical resistance. Cheap stuff, but great for winding coils on plastic.

Mica: excellent abrasion resistance at low temperatures (130 degrees Celsius - Class B). You don't see it as often anymore.

Polyamide (also known as nylon): good abrasion resistance at low temperatures (usually below 155 C - class F). Very common in motor cables. It is often used as a coating due to its abrasion resistance and low friction properties.

Polyester: High temperature resistance (often 155-200 - F class), poor abrasion resistance. Sometimes insoluble coatings must be removed chemically or by burning or cleaning. Often combined with polyamide.

Polyurethane: Mild temperatures (155-180 C - classes F and H). It is often used with nylon as a wear-resistant coating. Good abrasion resistance.

ML - Polyimide (not to be confused with polyamide) - very high temperatures (up to 240 C - class H), excellent chemical resistance, good abrasion resistance. It is often combined with nylon (polyamideimide) to improve abrasion resistance.

Polyamideimide: very high temperature resistant (200-240 C - classes F and H), high abrasion resistance. When used for non-solderable wires, the coating must be removed by abrasion due to the chemical resistance.

Some examples of wires.
Radio Shack - Formvar Polish (105 degrees Celsius)
GoBrushless Newbie - DBHPN - Double Nylon (155 degrees Celsius)
Micro Dan - Polyester/Nylon (180 degrees Celsius)
Belden CDT - Polyurethane/Nylon (155 deg C)
Dearborn CDT - Polyester/Polyamideimide (200 deg C)

So the next time you buy cable, maybe this will help you find the best cable for your motor.