The general consensus is that Southern railroads would be superior to OTL in quantity and quality, with resultant benefit for regional industrialization, bureaucracy, managerial control, and public interest in promoting technology and the mechanical arts. Of course, this would both aid Confederate mobilization and defense on 'interior lines', but also facilitate Federal invasion.
Georgia and Alabama would flourish exceptionally in regard to industry, especially if the planned and proposed railroads in Central Alabama, designed to exploit and tether the 'mineral region' of present-day Birmingham to Montgomery and Selma, can be completed as rapidly as the average Southwestern line in the late 1850s amidst the booming competition between Charleston, Mobile, and New Orleans. This road-building program was also designed to limit sectionalism within the State by commercially-connecting the Tennessee (appreciably Unionist IOTL), Alabama, and Coosa River Valleys. Rail communications from Chattanooga to Vicksburg would in general be more direct and short, rendering Joseph E. Johnston's OTL Western Military Division much more viable in regard to inter-departmental re-enforcement between Tennessee and Mississippi.
Crédit Mobilier would remain Duff Green's 'Pennsylvania Fiscal Agency', which will proceed with its international scheme to consolidate the transcontinental 'Southern Pacific' route projected to connect Washington, D.C., and the Mexican Pacific coast. The trans-Mississippi roads will require much labor, especially State-contracted slave. Indian and bandit raids would also be an issue on the frontier.