As far as choosing a corporate color goes, I would said neither RGB or CMYK. Rather, go for a Pantone color and derive the RGB/CMYK values from that.
The Pantone Solid Coated color libraries are available in both Illustrator and Photoshop, but truly you should select the color from a physical swatch. A local paint store might have the color book available for you to peruse.
There are some Pantone colors that cannot be represented using the RGB or CMYK gamut, however you can close enough that it wouldn't be distinguishable unless you were really trying to compare. The Color Bridge will tell you if they can or cannot be represented in RGB or CMYK.
The Pantone Color Matching System is largely a standardized color reproduction system. By standardizing the colors, different manufacturers in different locations can all refer to the Pantone system to make sure colors match without direct contact with one another.
A majority of the world's printed material is produced using the CMYK process, and there is a special subset of Pantone colors that can be reproduced using CMYK. Those that are possible to simulate through the CMYK process are labeled as such within the company's guides.
However, most of the Pantone system's 1,114 spot colors cannot be simulated with CMYK but with 13 base pigments (15 including white and black) mixed in specified amounts.
As a note, converting a Pantone color to RGB is not straightforward either. The RGB/CMYK values for some Pantone colors can be different in Photoshop and Illustrator, strangely enough. Example:
For PMS 350C, we've got 1 Pantone color being represented as two different CMYK values and three different RGB values between two Adobe programs.
So, my final thought: don't fret too much about achieving perfection between color models, you will just drive yourself crazy. Do, however, set a standard and stick to it.