Proprietary tools are almost ALWAYS much more expensive than their open-source counter-parts (yet for most of them, they USUALLY work MUCH better than their knock-off counterparts). For some, it's a way of establishing their "specific firearm kit", including most of the BRAND NAME ITEMS (including tools, accessories, etc.), ALL TO SAY that you're using everything that's COMPANY BRANDED. This will bring a higher price if and when the primary item is sold, because they WILL NOT sell the primary item without the accessories you've acquired in an effort to increase the value of the package for your sale to those who are looking for a complete package - all because they don't want to take the time and trouble to look for the items themselves.
I know. Way back when, I was a slave to things H&K and items surrounding the HK-91. I bought MANY of the brand-name accessories, including cleaning kit, bayonet, multiple magazines (EXPENSIVE), and many non-H&K items too, like a fitted plastic brass catcher, a rubberized ejected-brass buffer to keep the cases from being dinged, a collapsible stock, I had factory tool, tool kits, etc., all of which I paid good money for to ensure they were H&K items. It was a COMPLETE set-up.
And when I sold it ALL (including ballistic-nylon rifle case/drag bag with external magazine pouches) right before the damned CA Assault Weapons Bill went into effect, at a 100% profit (more than DOUBLE what I paid for everything). Had I known what else was coming, I wouldn't have sold it and kept it, even though my wife (in the process of divorcing soon at the time), but I doubt she would have turned me in simply because she didn't know about the gun laws and was more like a monk, ignoring everything legal going on around her as the world went by, since I always took care of everything else.
To this day, I continually kick myself for selling my COMPLETE HK-91 setup. ARGH!!!!!!!
So, keep in mind your goal. Do you ONLY need the tool to get the job done, or do you think (even later on) that it might be more valuable in the years to come if it's a proprietary tool made by H&K. For some of this, only time will tell, but if you have clear goals of only getting the job done, then by all means use/get the cheaper tool.
YMMV