Yes, it's in relation to the size of the kite. Bigger kites will turn much slower on smaller bars, because there isn't as much 'throw' on a small
bar. People keep smaller bars for smaller kites so that they won't oversteer the small kites.
This is an extreme scenario, but for visualization purposes only:
(WARNING: DO NOT ATTEMPT TO FLY YOUR POWERKITE WITH A TOOTHPICK)
Imagine having a toothpick attached to a 10m foil. The difference between turning it like this: _ and this: | isn't going to be big enough to pull
one side of the kite in and let the other side out to turn it. Then replace the toothpick with a yardstick attached to the same kite. You'd be able
to turn the kite on a dime because of the huge angle difference between the side of the kite you're pulling in, and the side of the kite you're
letting out.
If you only have a bigger bar and wind up using it on a smaller kite, you could keep your hands close to the center of the bar to minimize
oversteering. If I were you, I'd keep one big and one small- just in case
Kites:
2012 TS 7,9,12/2007 Waroo 3,5/2009 Kahoona 9.5
Flexifoil Ion 2 8.5
HQ Hydra 350
Naish Helix 2, Cult 3,4.5
Ozone Zephyr 17m
Rides:
2011 Best Profanity 134, Cabrinha Kiteskate, Cabrinha Nugget, 2k9 Cabrinha Plasma 146x50, 2k9 Flexifoil Delta 139x41.5, 2011 Slingshot Darko 135x41,
Slingshot Scud, Tona wakeskate, Flexifoil Flexdeck, MBS Pro 90, MBS Ambush x 2, some oldskool buggy