Simple test...pick a #5 and a 5-1/2 up, one in each hand....see how long before one is set back down....
Momentum might be nice....until you have to drag the plane BACK to the start point...after awhile, that extra weight gets old.
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Of the four #5 sized planes, this one has the most camber, as it is used for this sort of thing..
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There are also two Stanleys, each a little less camber, one having none. There is a Millers Falls No. 14 that barely has any. My #5-1/2 has no camber, nor does the #6 or #7...Then there is Mister Everything....Millers Falls No. 11, a #5-1/4 sized plane. Small jack, light and nimble, no camber. Smoothing is done with either the Stanley #4c, or one of the smaller Millers Falls planes.
I used what best suits the size of the work being done.
A small smoother can "turn on a dime" to deal with reversing grain.....a No. 5-1/2 cannot. Almost like trying to spin the USS Iowa around at speed....compared to a Coast Guard Cutter...