We'll be walking in circles forever with all that hybrid vs. old beater, and it all started with batteries and their environmental impact...
Considering the energy spent in mining for rare earths used in electric motors, and either Nickel or Lithium to the batteries, then the logistics, both the energy balance and the pollution footprint from a battery pack is often pointed out to be even higher than the footprint of a Hummer H2 in a 20-year life cycle, even after the energy required to refine petroleum and to transport the gasoline is taken into account. Sure it sounds weird and over-exagerated, but if we could consider something with an engine smaller and lighter (thus requiring less raw materials) than the Hummer's V8 I'd still rather get an old Mercedes-Benz MB 180 D with the die-hard OM616 engine rated at 79hp instead of a brand-new Prius.
And while you would need a computer to be hooked up to the Prius, I could fix anything in the old Mercedes just with manual tools.
Sure there are other old beaters that could be compared to the Prius more closely than the MB 180 D, either gassers like the Metro or small Diesels like an early Rabbit. Even a current Golf TDI could be compared to the Prius if you would rather want to compare brand-new rides, and we might not forget that it still has engine options more efficient than the U.S.-spec 2.0L in overseas markets.