Lightmeters - which is best?
The light metering capabilities of modern DSLRs combined with an understanding of exposure will get you well exposed ambient light images without the need of an external meter. In fact using the camera metering system and using the Expose To The Right technique will give you a better exposure than the one you get from an external meter. Here is my tutorial on using the camera's Highlight Alert to make ETTR easier.
You can also use the camera metering system to get good flash exposures but the transient nature of flash (strobe) lighting and the need to adjust the power of flash lighting to give you the correct exposure makes this more difficult. Using an external flash meter will make setting the flash power to give you the correct exposure much easier and faster.
If you are looking for a flash meter then the Sekonic L-358 and the Gossen Digipro F are two I can recommend. Both can be recalibrated to correct for any drift of the meter with time or if your camera shutter speed and/or lens apertures are not accurate. Both meters will read ambient light in either aperture priority or shutter priority.
The Sekonic L-308 and the Gossen DigiFlash are lower priced quality flash meters but they are not as flexible as the L-358 and Digipro F meters. They can not be recalibrated and they will only read ambient light in the aperture priority mode.