Why? I have no idea, midlife crisis is my best guess. Anyway, here are my overall impressions.
The Zebra G-450 is the smoothest with the least amount of drag. It’s made of metal and has the most solid construction. This also gives it the most weight out of all the pens and feels good when you pick it up. The disadvantage is this pen is thinner than the other pens. It was the hardest to hold for longer periods of sustained writing. The click action was also rather anemic. If it were a little thicker, it would easily be the best pen.
The Signo 307 feels very fast, and overall it is a very smooth writing pen. It feels good in the hand and has a positive click action.
The Sharpie S-Gel has the most drag out of all the pens. It has a good feel in the hand and is the most comfortable, but is the worst at writing.
The Pilot G-2 was the second smoothest pen, it also did not drag. It does have a cheaper feel to it with a clear plastic body but is comfortable to hold for longer periods. The line is a little thicker than the rest of these 0.7mm pens, and the edges are slightly blurry compared to the crisper edges of the other pens.
What have I learned? I like the Zebra G-450 and Signo 307 pens, and I really need to take a good long hard look at the direction of my life being that I just posted a pen review.