the vbar is a part of the equation, but after five seasons on a flybarred logo 600 and a couple years with the FBL logo 600, I think its a small part.
The flybarred head is second only to the Hirobo fz5 and can be tuned to perform. I've also owned the logo 14, its the parent of the logo 600.
The logo 14 (as is) could only take mini servos and has a two stage tail transmission, small gears, a thin boom, and a flimsy canopy...guys were hot-rodding the 14 with normal servos and mod 1 gears, basically making a v1.0 logo 600.
The logo 600 use of plastic to make a same curved frame concept as the logo 10 and logo 14 that is large and light is the core of the difference between a logo 600 and every other 600
After that, the 1 inch thick boom is a big difference. It is much easier to see and allows a single stage tail take-off with a larger output gear in a typical fore-aft frame dimension so there is less friction...much less than the logo 14 two-stage which is a typical separate belt system.
The kicker that makes this heli even better on top of all that is the gearing options.
There isn't another 600 with as many gearing options...so it is light and can work with just about any motor around.
...so why do I have over 1,500 flights on my flybarred logo 600? because until parts run out, I haven't seen a better balance in price, performance, and options ever made. Even the rest of Mikado's helis can't compare to the home-run they made with the 500/600.
The airframe is only about $200 more than a crappy 600, can run on the crappiest batteries and average motors, blades, and use the same electronics as any 600...whats not to like?!