OK real numbers time. The 40 S&W Glock 27 verses a two inch barrel 357 MAG. If you measure the revolver the same way as you measure the auto the 2" revolver barrel plus the cylinder measures 3 5/8 inches. The Glock 27 has a 3 1/2 inch barrel. As you can see from the photo below the two pistols are very similar in size.
From my own average velocity readings:
My Glock 27:
155 Speer GDHP................1106 fps / 421 energy 76 momentum
165 Win Ranger T..............1093 fps / 438 energy 80 momentum
180 Win Ranger T...............896 fps / 321 energy 72 momentum
180 Rem HP.......................947 fps / 358 energy 76 momentum
My Rossi 357 MAG:
158 PMC SJSP.................... 968 fps / 329 energy 68 momentum
158 Federal SJSP................1022 fps / 366 energy 72 momentum
125 Federal SJHP................1145 fps / 364 energy 64 momentum
The 357 Mag and the 40 S&W are similar. The 357 will really come to life and out power the 40 in longer barrels but the 40 out powers the 357 in shorter barrels. Also the 40 does have the advantage of having a wider bullet.
My carry load for the Glock 27 is the mild Winchester 180 grain Ranger T.
My carry load for the Rossi is the Federal 125 SJHP 357 MAG.
I also have a 5 1/3" barrel Glock 35. My carry load is the Speer Gold Dot 155 grain that does 1245 fps / 533 energy 86 momentum.