To be fair, one should discuss figures to give an answer. Ferdinand's economical stance had been all along resumable in two concepts: low taxes and a balanced budget. No sign of agrarian reforms nor policies to encourage industrialization. Sicily was treated nearly as a Neapolitan colony. While the first Italian railway was the famous Napoli-Portici, by 1860 the KoTS had a mere 100 km of railways in contrast to 1800 of the rest of the peninsula. Which tracks were favored then? Napoli-Caserta, and generally speaking, the network did not expand far from Naples: no link with the other major cities in the Kingdom, and not a single railway in Sicily. There were some industries, some excellent, this is true, but I am not sure that cotton in Salerno, wool in the Liri valley, and colour, paper and leather could become an industrial powerhouse. Pietrarsa was a big mechanical centre, but it was state-owned AFAIK and served for prestige and military. Generally speaking, Ferdinand of Bourbon was no economist and he thought he administered his state in the best possible way, seeing no point in improving. The technology he liked (the telegraph network was considerable by 1860) was for prestige and if served his scopes, science for science's sake wasn't exactly his creed. So, say that somehow his son Francis II manages not to lose his kingdom (not to be rude, but he was the kind of guy who did not lose his head just because it's on top of his neck), things would just keep going this way in the Two Sicilies, or maybe worse since Ferdinand had done some decent things in the early days of his reign, I doubt Francis could do anything well.
WARNING: this is not to say that the Piemontesizzazione was not bad. Italian unification was really badly managed and it had some dire consequences for the South. However, IMHO this does not change the fact that one would need a radically different reign of Ferdinand of Bourbon to have the South with a bourgeoning economics to rival the North, which has some clear advantages: Po valley, plenty of rivers (both for communication and to generate power), closer to European markets.