I agree with Beagle333, less built up pressures.
My test was with the .44 mag.
Lubed lead - Missouri Bullet - .44 E Keith - .430/240 grain/18 Brinell.
Coated lead - Lyman 429241 - My hard mix lead (don't have a tester, every bit as hard as the 18 Brinell above), no gas check installed, actually bullet weight is 245 to 245.5 grains - sized to .430 both before and after coating with HF RED.
The weapon - S&W Model 29-2 6 1/2 inch.
The load - 17.5 grains of 2400, (what I call a) medium role crimp, CCI 300 Standard LP primers, Star brass.
Velocities at 10 feet.
The readings. The lead loading is an average of (well) over 15 test samples. The coated loading was only 12 test samples (15 samples are my standard for good statical results.)
Lubed lead - 1294.1 FPS
Coated lead - 1096.333 FPS (the first 6 gave an average of 1112 FPS, thus I ran a second 6 to confirm)
That is 198 FPS slower. With the lead loads I get no leading and perceived pressures are acceptable. With the coated loads I get no anything less a few puffs of powder ash and perceived pressures are less than those with the lead loads. I believe that I could up the charge with the coated lead and equal and exceed the velocities of the lubed lead loads. But, I'm happy with what I'm getting with the Missouri Bullet lubed lead bullets.
Standard disclaimers, safe in my weapon/s the way I load with my components. May not be safe in yours, the way you do it with your stuff. This is for information only, not loading data.
Load with care,
OSOK