Woops, I got it very much backwards!!
Yes, yes. More mechanical advantage means more power
and more mushyness in the feel of the brake lever. See Sheldon Brown's excellent write up here. In particular, he addresses this in the "Feel vs Function" section.
http://sheldonbrown.com/cantilever-geometry.html
IME, caliper brakes go from lower mechanical advantage (feel crisper) to higher (feel mushier) as follows:
+ Single pivot side pulls
+ Dual pivot side pulls
+ Centerpulls
As Sheldon (and others) note, canti brakes have adjustable mech advantage when you adjust the straddle cable to different lengths. Longer means less. Shorter means more. I think this suggests why Weimann/DiaCompe c-pulls can feel mushy. They have comparatively short straddle cables and hence even more mech advantage.
If the OP is using modern Aero style levers, which them selves have more mech advantage than non-aero levers, then he's adding even more mushiness to the system. Sheldon correctly warns that too much mech advantage and you can bottom out the lever on the bars before the brake is at full power.
My c-pulls are set up with similar vintage non-area levers. They feel mushy compared to my single pivot side pulls but they definitely stop fast. And again, following Sheldon's observations in his essay (above), the difference the 2 brakes compress the shoes is quite visible on the work stand.
Sorry for the confusion. I got it way wrong on that other post!!