Full Throttle at low RPM, or High RPM and low throttle

[Lorena_Palin]

so I just got in from a night of driving my mom's 1997 Subaru legacy (not outback) wagon around with the fuel needle just above empty. It's a 5 speed, and has god knows how manny censors and such dead in the engine, but at just under 200k miles, I'm lucky it's running.

Anyways, I know the IDEAL thing to do is to barely tap the gas pedal and shift as low as you can without making the engine knock/ping or stall. However, because this car has lost alot of horsepower over the years, to the point where in 5th gear it takes about 30 seconds to go from 60 to 65 and it tops out around 75, and the fact that around here you kind of have to be able to zip out into traffic, I'm wondering, which is the lesser of two evils? Shifting at a higher RPM but not putting your foot all the way down, or Jamming it to the floor and shifting at around 2,000 rpm?