In this situation, an ohm resistance of less than 1 would be better than an ohm resistance of greater than 1 for heat generation. This is because the power dissipated by the glow plugs is proportional to the square of the current passing through them, and inversely proportional to the resistance of the plugs. This is expressed by the formula P = I^2 * R, where P is power, I is current, and R is resistance. Therefore, a lower resistance value means that the plugs will allow a higher current to flow through them, resulting in more heat generation.

In your case, the glow plugs with a resistance of 0.7 ohms will generate more heat than the ones with 1.7 ohms, assuming the same voltage is applied to both sets