I have a DRY (3x 18650 side-by-side) and a WF-500 (2x 18650 end-to-end). The 500 isn't awkward to carry in the hand, but it is not pocketable for most pockets. The Dry is pocketable if you have loose pockets (no tight jeans). The Dry is comfy to carry in the hand (I have average-sized hands). The 500 can be flipped back and forth from underhand to overhand grip quite easily, and that's what I do when I need to click the tailcap switch with my thumb. The Dry is more difficult to switch between grips, so I had to figure out a way to click the switch with my 4th or 5th finger. This is not ideal--I would much prefer a rotating selector ring near the head.
I think the 500 looks okay, but I think a 3x 18650 end-to-end light looks weird (just my opinion). Since I'm interested in high-output lights now, I need 3x or 4x 18650, so that means stubby fat lights.
Member 2100 once mentioned that the TK70 can be awkward to use, because it cannot be swung around quickly. There's a term for that but I forget what it is. "moment"? Imagine holding a broomstick. It would be hard to swing it around quickly, compared to a stubby light.
If you get a stubby light, some connect the cells in parallel, and some connect the cells in series. With a long skinny light, they're of course always in series.
If you want a single-LED light, a long skinny body would be fine. But if you want a 5-or-more-LED light, the head might be so large that it looks like a toilet plunger on a long skinny body. If you want a multi-LED light with large reflectors (for better throw), the head will be even bigger. Look at a picture of the XTAR S1. If it used 3x 18650 end-to-end, that would be a weird looking light.
I think a side-by-side arrangement requires less mass in the body tube than an end-to-end arrangement, but I've never done the calculation. The way I think of it, adding another battery in an end-to-end arrangement means adding a whole section of body tube. But adding another battery in a side-by-side arrangement means just adding a "strip" to widen the diameter of the body tube.
I think for a 3x or 4x side-by-side body, a selector ring or side switch is mandatory. I can use the tailcap clicky on the Dry, but it's awkward.
The stubby light will tailstand much more stably than a long skinny light.
The long skinny light is much more effective as a club.