With the differential capacitor version you can't have both capacitors at maximum (or

minimum) at the same time. That may limit your matching range at the low (or high)

ends of the range. Specifically, for the same maximum capacitance value, the

efficiency will be lower when matching low impedance loads because you can't get

as much capacitance into the circuit, which forces higher circulating currents. This

is primarily a problem on 80m and 160m.

In my experience, most of the time I can get a match with one or the other

variable capacitor at maximum capacitance. If so, this will be very close to the

point with the lowest losses. With one capacitor at maximum, adjusting the other

one and the coil is no more difficult than juggling the coil and differential

capacitor. (And I put stickers on the face of my tuner to mark the dial settings

for each band, so it doesn't take very long to retune anyway.)

Does it make a big difference? Probably not if you mostly work 40m through 15m or

so. You can see for your self using W9CF's handy tuner simulator applet here:

http://fermi.la.asu.edu/w9cf/tuner/tuner.htmlYou can mimic a differential capacitor by assuming that both capacitors have to

sum to a fixed value, which is the maximum + minimum values. So, for example,

if your tuner has 250pf capacitors, assume that the two capacitors have to add

up to about 265pf. Then you can try matching the same load both ways and see

how much difference it makes.