Apple apparently disappointed the fans of its small 13-inch professional notebook by denying the revised 13-inch MacBook Pro version an upgrade to Intel’s latest processor architecture – an update that has been introduced in the new 15-inch and 17-inch MacBook Pro versions.

While the 13-inch MacBok pro retains the Core Duo 2 processor, its bigger-screen counterparts have been updated to Nehalem-based cores, along with 32nm, boasting definite performance enhancements for Core i3, Core i5, and Core i7 mobile processors.

Among the several reasons why Apple denied the improved processor advantage to the 13-inch MacBook Pro model apparently include - cost, graphics performance, and battery life.

The 13-inch MacBook pro is Apple’s smallest ‘professional’ laptop, and to retain its light and ‘affordable’ tag, the company has stuck to the basic architecture of the preceding models – a Core 2 Duo processor, which is cheaper than both the Core i3 and Core i5; and a NVIDIA GeForce 9400M controller with integrated graphics.

According to the information forwarded to Ars by an Apple spokesman, Apple clearly had no intentions of crippling the 13-inch MacBook Pro by having it “stuck” with Core 2 Duo technology. Rather, the company the notebook and upgraded processor largely to maintain its unique combination of portability, performance, and extended battery life, at the existing $1,200 starting price.