Allright....some serious plane talk,haha.
Speed......and how it apply's to or in the shop:The faster a job gets done,the faster we get paid.That there,is a forgotten or somehow....missed application in shop world.Yeah,yeah.....we "think" we're fast,in todays world,but we ain't hittin on chit compared to the craftsman of yore(thinking handtools).
Speed and handtools was the end-all,be-all back in the day.So,if Stanley made an aluminum 78.....which I didn't know(thanks)...then I can certainly see it's value.To wit:we'll give up a little durability because of speed?It boils down to how much $$ is this handtool gonna make me?
But going past pure speed for a second.....a grooved bttm gives more feel.And it ain't just on softwoods.......Just like racing tyres,planes operate at a "slip angle"..."C's" have more feel when used at an angle.Its each "edge",biting in at this slip angle that makes the overall pkg "quicker".Smooth bttms have this sort of slushy feeling.....you never get the "bite" that the C's have.This is all based on the premise that we're not planing directly parallel to bds axis.......they really prefer you to be at around 5 to 10 degrees.The smooth bttms tend to "fall off".
Another aspect of planing is to "lift" the plane.....just like a file...on the return stroke.So just like aluminum 78's.....a true craftsman will always utilize the lightest plane that gets the job done.Read that....2's and 3's(and to a lessor extent,"C's')over something larger.Its a nuance that again got lost somewhere...in the "bigger must somehow be better",world that we live in.