If you were me, you'd opt for the 10-shooter --- no greater weight, girth, or any other downside, they're both equal in ejection speed, and the 10 round cylinder holds 66% more ammo. Now, if you extend this out over the projected life of the weapon, assuming it's passed on over the next generation or two, why, just think of all the man-hours saved by going with the ten vs. six round version. It makes me weary, just thinking about the amount of time that might be wasted in the needless, tedious, reloading of the six-shooter, holding only 60% of the ten-shooter's capacity! I'd say you owe it to your heirs, successors, or assigns to go with the ten, even if you have no regard whatsoever for the time you, yourself, may end up wasting with a poor choice...
This is of course not to even mention the unnecessary additional wear and tear on all the parts involved in opening and closing the cylinder/crane assembly, were you to choose the six round vs. ten round iteration...
My ten round 617 is one of the most "fun" guns I own, and statistics aside, I'd guess that it would be among yours, as well.