The 327 mag runs 1400fps with a 100gn slug, the 357 goes 1400fps with a 125gn slug, that would be more, not comparable. Many people consider the 327mag a solution in search of a problem but I say it solves two problems. One, it makes mundane guns like SP101s collectable and two it's a chicks 357.
Where are you getting your data?
I think you're comparing unequal barrel lengths, and fudging the comparison.
On a cold day, my brother's SP101 will sling .327 Federal American Eagle 100 gr SP factory ammo at 1,500+ fps. On a warm day, it'll push it 10-15 fps faster.
Out of my 5.5" Blackhawk, that same load is doing 1,680 fps on a cold day, and in excess of 1,700 fps in the blistering heat of summer.
If you're comparing "factory ballistics", cite your sources. Most ammunition companies use an 8", or 10" barrel for their velocity claims. It sure does look good on paper.... until you look up the barrel length, and realize what a joke the claim is.
Keeping your 100 gr .327 vs 125 gr .357 comparison-
In reality, the .357 needs an 8" or longer barrel to reach the same velocities a 3" barreled .327 can produce.
For the .357 Mag, the "standard" load is 158 gr bullets of various types. The 125 gr loads are (125/158 = 0.79) 79% of the "standard" weight.
For the .327 Federal, the "standard" load is not quite settled, but arguably 100 grains. A 71 gr FMJ comes in at 71% of the "standard" weight.
I can shoot 71 gr FMJs in excess of 1,800 fps, from my 5.5" barrel. The .357 Mag requires a ten inch
barrel to do the same with a 120-125 gr bullet.
If you don't like the cartridge, that's fine. You don't have to. Don't go throwing out unsupported claims, though. It just makes you look ignorant and uninformed.