Well to begin with when your talking about line length between the two brands your basically talking about a moot point considering there isn't enough difference between the maximum line length to make a difference in anything you would trim. As 066 already stated anything longer than max length will only effect the clutch, drive shaft, gear-head wear and affect engine performance.
If your looking for more cutting power and effective cutting power with the maximum line length you have, I'd suggest you start looking at the engine spec's and see what machine offers the most effective engine power between the two brands.