Shootability. In this case tho it's the intense blast that .327 Mag has, it's on par with .357 Mag. Also, .327 is a very good penetrator, verging on overpenetration at times due to its velocity and sectional density, .32 H&R Magnum is less so because the velocity is a bit lower.
As you know, I'm a proponent of .32 in small, light pocket pistols over .380 for the reason of shootability because there is a difference between the two in a 10oz pistol, there is a difference between .327 and .357 in a 20oz LCR and 30oz SP101, but there is no difference between them in a 40oz GP100, at least not enough to warrant using a smaller bullet and I would say that even if the GP could hold 8 or 9 shots of .327 vs the seven rounds the .357 holds.
Conversely and hypothetically, if someone made a .32 S&W or .32 ACP in a 5 shot and it weighed say, 6oz, and was smaller than even a J frame, I would buy it over a 5 shot .38 or 6 shot .32/.327 Magnum snub because I'm not buying it strictly for the caliber, I'm buying it because it's a smaller, lighter gun in a caliber that I trust more than .22 rimfire.
I guess what I'm saying is that big guns should be in big calibers, small guns in small calibers. Small calibers in big guns and big calibers in small guns are like a marriage at a 24 hour chapel in Las Vegas: it's just not meant to be.