* Speed: The Z28, with its LT1 engine, typically had a slight edge in acceleration and top speed over the SS and its LT1. While both used the LT1, the Z28 often had a slightly more aggressive gearing or other minor tuning differences resulting in a performance advantage.
* Cost (new vs used): When new, their prices were relatively close, with the SS potentially commanding a slightly higher price due to its more luxurious features (though this depended on the options selected for each). Now, used car values fluctuate wildly based on condition and desirability. A well-preserved, low-mileage Z28 might be more valuable than a comparable SS, or vice versa. The collector car market dictates current prices. You'd need to check current listings on sites like Bring a Trailer, Hemmings, or Craigslist to see the current market value.
In short: The Z28 was likely faster in 1994, but price differences today are unpredictable and depend on the used car market.