After handling both I prefer the longer handguard, can get a grip further out and better for mounting a bipod. Gives a little more space for other accessories and if you want to run irons a longer sight radius. Slightly more weight but for the aluminum handguard it’s not perceptible.
The biggest difference in that M10x models is the heavy vs light profile barrels, that makes a difference, ideally I would have a long handguard and light profile barrel. I also think the longer handguard looks better and more proportioned vs the short, but that’s personal preference.