Supposedly the reason for the "steel" brake lines is that under high pressure (ie panic stop or heavy braking) the rubber lines will expand causing you to lose some hydraulic pressure. The steel lines won't expand and therefore the hydraulic pressure from the master cylinder is completely transferred to the calipers. Or something like that 
Deron
'99 Tropic Green SVT #924/2760
K&N, Mobil1, '98 Clock, dual horns,
SHO Shop Rear Strut Tower Brace,
BAT Rear Sway Bar Bushings,
ST200 Shift knob, Pioneer TS-A6855
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