By the way, what's the difference between Socialist and Socialist Labor?
The SLP was a dogmatic fringe party whose members were mostly German-speakers. It rejected social democracy and social and economic reforms, in favor of structural changes in the economic system brought about by industrial syndicalism. The SPA was a more traditional social democratic party, with considerably more support among English-speakers. The SPA aspired to be more of a big tent, de-centralized left-wing party, unlike the SLP which was a very doctrinaire, top-down party run by Daniel De Leon.
Not just a new economic system, DeLeonists wanted and (the few that still exist today) still want an entirely new form of government. They called for the All Industrial Congress and a host of other major changes, which would have necessitated a new constitution.