We explore the spectrum of strong consistency transactional protocols, using both formal properties and performance, in a common framework (based on Deferred-Update Replication) called G-DUR. In G-DUR, a high-performance transactional protocol can be implemented by mixing-and-matching appropriate plug-ins, corresponding to formal properties, in a few hundred lines of code. Therefore, G-DUR enables an apples-to-apples empirical comparison of protocols, and enables studying their limitations and possible extensions, by substituting plug-ins. In this way, we identify four important performance properties. Finally, we describe NMSI, a protocol that satisfies all four properties, and we show that NMSI has the best scalability and performance among strongly-consistent protocols, matching that of a weakly-consistent protocol.