It's not that you would load a similar font, under the windows regime, the OS loads a similar font if it can't find an exact match! Then it cheerfully goes on about your business as if what it did were perfectly reasonable. GRRRR! Sigh!!

Typically the difference between italic and oblique is that an italic font is designed to slant, while oblique is just knocked up the side of it's head and made to tilt. Use italic over oblique is best from the typophile point of view.