For me the Mechanical Reliability is questionable
The CON-70 that came with my pen started out with a sticky plunger that only got more sticky and then failed. My Falcon nib goes through ink quickly. So I ordered a replacement CON-70 for its ink capacity. My new CON-70 button movement is not as smooth as I was hoping it would be. But it is a lot better than my original CON-70. I've used the CON-40 in my Namiki Falcon for about 7 years with no issues. In the future I think I'll switch to the CON-40 for its mechanical reliability and replacement price point. Having to refill my pen a little more often CON-40 will only offer me more frequent opportunities to change the ink I'm using.