I've owned, handled and shot both the 5906 and 5903. I've always felt the 5906 with its steel frame is overkill for the 9mm cartridge, just too heavy and cumbersome for a 9mm. I eventually sold the 5906. On the other hand, the 5903 is a delight to handle and shoot. It is, IMHO, well balanced and quick to respond. In short, a great medium frame 9mm.

Oh yeah, it shoots pretty darn good, too.