)

From the point of view of the Italian Fleet, the battle definitely wasn't a "substantial victory" to the Italians in any way. 
However, almost all sources agree that, had the Italian Battleship and Cruisers remained at anchor, or had the Italian ships failed to make contact with the convoy, the British delivery of supplies would be completed according to schedule, namely, before sunrise. This disruption of the Royal Navy plans, along with the damage inflicted upon the escorting units, made the cargo ships an easy prey for the German and Italian torpedo-bombers the morning after the battle. 
The only cargo ship to make Malta undamaged by the bombs was the Talabot, largely overdue from the original timetable. All the other were hit in some degree by axis aircraft BEFORE reaching the harbour (not just Clan Campbell, which means that the Royal Navy was still responsible for the steamers fate), further hampering the escorts effort to disembark the supplies in time. 
So, despite the remarkable skills of the British units to save the merchantment from an attacking Battleship, the naval engagement should be considered a marginal victory to the Italians. 
On the other hand, had the British deceived their enemy or in some way avoid major contact with the Italians and reached La Valetta at dark, yes, the Royal Navy success would be undeniable.
 00:52 February 28 2007 (UTC