The powder's original form is a longer grain stick, while the short cut, as the name implies, is a shorter stick, with some modification to the powder formulation or to the grain perforations so the burning rate isn't increased by cutting it shorter.
Short grains usually meter to a more consistent throw from a powder measure. However, the longer grains usually ignite more readily. If you are weighing charges rather than throwing from a measure, I would get the longer grain version if I could. Even if you are throwing from a measure, the ignition superiority may still outweigh charge precision as in the example below. You just have to try it to find out.
In Hatcher's Notebook, Gen. Julian Hatcher describes working up National Match ammunition one year (the Frankford Arsenal used to roll all the ammunition used at the National Matches back when they were still considered a function of military practice for civilians that might one day be drafted) with powder candidates that boiled down to a long grain and a short grain powder, both similar to what later became IMR 4320. The powder metering on the arsenal loading machines could hold the short grain to an extreme spread of 0.6 grains in charge (+/- 0.3 grains), while it could only hold the long grain version to an extreme spread of 1.7 grains (+/- 0.85 grains). The former is decent even by modern commercial standards, but the latter is well below what home reloading measures today will do. Nonetheless, he said that in machine rest test firing, the coarse grain loads, with all that variation, produced consistently more accurate ammunition than the more accurately metered fine grain loads, and was selected to load that year's National Match ammunition.
Hatcher said some know-it-all at the matches that year pulled down enough of the ammunition to discover the wide charge variance, and declared that it was no good. This fellow conveniently ignored the fact several records were set with it that year. Hatcher believed the accuracy had to do with the superior ignition characteristics of the coarse grain, which lets the flame front move freely through the large spaces between the grains. The explanation goes no further, though others have observed some of the IMR powders seem to be less "pressure sensitive" than some others. The ability of IMR 4895 to produce accurate ammunition even in load densities as low as 60% being one of the better known examples.
So, you can't be sure without testing in your gun which powder cut will really do best? You'll have to run them side by side. My concern about the SC and SSC versions of some popular powders has been that they were concessions to complaints by fellows like the one who pulled the ammo at the national matches in Hatcher's tale, and not that they actually demonstrate better shooting performance. But that could also be wrong. Like all things for reloading, you just have to do a side by side with your loads and equipment to see how they do for you, and not for some theoretical consideration?
Sierra's manual lists only the IMR 4831 SC version with the 130 grain SBT, but the load should apply to both. If you have both powders the lot numbers will be different, so they would have to be worked up separately if you want to compare the two? [EDIT: BAD DATA REMOVED per error noted in following posts] In Winchester cases with Winchester WLR primers, seated to 3.300" COL, they list H4831 SC 52.1 to 59.2 maximum. The load was developed in a Savage 116, and not a test barrel, so the chamber was not likely a minimum chamber. That means, if your chamber is tight chamber its maximums may be lower. I would be tempted, for that reason, to start at more like 61 grains, just to be sure, and watch carefully for pressure signs during load work up.