Well, the data is a bit suspect.
You need to understand the regulator's internal circuit before you try to interpret the meter readings.
Between BAT and GROUND there's the relay coil; this is a voltage sensing relay that's supposed to open its contact at about 13.5 volts. The contact connects BAT and FIELD when closed. There's also the 10 ohm resistor between BAT and FIELD all the time, the relay contact is in parallel with it... so between BAT and FIELD there's a direct connection below 13.5 volts and 10 ohms above 13.5 volts.
The resistance of the coil is fairly low, 10 ohms is fairly low, and the closed contact is very low resistance hopefully. So the meter readings may not be easily understood, particularly on a meter with poor resolution at low resistance (most any cheap meter, for example).
Electronic regulators mostly use some type of transistor to replace the relay and usually omit the resistor, switching at a relatively low frequency using pulse width modulation on the field terminal to produce a wide adjustabilty of the alternator output without producing a lot of internal heat.
There's no overwhelming reason to prefer an electronic regulator. The mechanical type will actually provide more field current than an electronic one; the relay contact can have almost zero resistance while all semiconductor current devices have an unavoidable voltage drop. The electronic ones should give better control over the system voltage. A charging system with other problems won't work better though.
The biggest trouble with the SOHC4 charging system is the wiring harness. The voltage at the regulator BAT terminal is at the end of a long series of bullet terminals and the ignition switch contact, many large loads are near the regulator end of that chain as well. With corroded terminals and switch contacts the voltage at the regulator will be several volts lower than the actual battery voltage, often this is too low to provide enough juice to the field coil to get good alternator output. If it is enough... then the battery voltage is so much higher than the regulator BAT terminal voltage that the battery gets overcharged and boils dry.
So the best approach to any old bike with charging problems is to clean all the bullet connectors. A good addition is a 12V headlight relay with the coil connected to ground and the regulator black wire (disconnected from the regulator) and a NO contact between the battery + and the regulator BAT terminal (this should be fused); this puts "real" battery voltage on the regulator so it's regulating the correct thing, and provides maximum available power for the field coil. My experience is that these 2 things will give you excellent charging with the mechanical regulator or an electronic replacement.
