You do get more responsive control on shorter lines. However, flying something like a 8m or 10m you'll want to fly on longer lines than something like
a 4m, since the turning radius is a lot wider on a 10m than a smaller kite, hence you need longer lines to be able to turn it.
Flying a 2m on short lines can be a handful though because the smaller kites turn so much quicker, so longer lines can give you more time to respond.
Serious buggiers who race will have a few different line sets of different lengths to put the kite in the best wind - i.e. if the wind is very low
they may fly much longer lines on a larger kite to put it up high in the clean wind. The opposite of this is that you can fly a larger kite much
closer to the ground on shorter lines in stronger wind - for example a 4m on 70' lines may be overpowering, but flying it closer to the ground on 40'
lines will give you plenty of grunt but not be overpowered.
Something else to bear in mind is that 150' of 300lb line has a lot more weight and drag than 70' of the same line - what you gain in better wind
higher up you may lose in the weight/drag of the longer lines.
There's no real 'correct' answer, just what works for you.
Quadrifoil Q2002 1.5m
PKD Century 2.5m
Flexifoil Skytiger 40 3.7m & Hi60 5.6m
PKD Century 4.5m
Pansh Blaze I 12.5m
1997 Flexifoil original buggy - a few weld repairs but still going strong :-)