Old or New? Debate Rages Over Transit Downtown
Pitched battle is already being waged behind scenes over $4.55 billion in government funds set aside for transit in Lower Manhattan, fueled by debate that could determine future of downtown; at issue is whether funds allocated in aftermath of terrorist attack should be spent only to improve existing transit or to bring in new train service that would make downtown more convenient to suburban commuters; diagram; proponents of new rail, including Sen Charles Schumer and Deputy Mayor Daniel Doctoroff, say downtown will not remain one of world's financial capitals without better links to region and airports; critics point out that city also needs money for several other huge, long-needed projects such as Second Avenue subway and LIRR link to Grand Central Terminal; Gov George Pataki is key to ultimate decision but has so far left issue to transit authority; chairman Peter Kalikow comments (M)