I shoot landscapes with a hand-held only. There's simply no point to using the built-in meter when I have time to use a hand-held. I use the Sekonic L-758. Why? Because I can calibrate the meter to my camera's exact dynamic range, within 1/10 stop. That range then displays on the meter so when I take a reading of highlights and shadows I can verify that the shot will record with all detail, and if not I know how I need to bracket for HDR, usually no more than two shots. The mistake most amateurs make is bracketing the hell out of HDR when almost no images require more than two to three shots.
The 758 also affords me a 1-degree spot meter, more accurate than any DSLR spot meter, so I can read a specific highlight and open up as desired from there. This also enables me to pinpoint highlight and shadow readings. There are too many other benefits to list. Some of them include instant averaging, instant calculations of stop difference between two readings (A light, B light), other quick calculations, flash metering for exact exposure every time, and the ability to quickly find the exact midtone of a scene.
One of the best benefits is incident metering. The incident meter is never fooled by brightness or color of the subject. It measures only the light itself as it falls on the scene, not what is reflected. Since it's measuring the light, I know tones will be rendered as they are under that light -- black as black, white as white. No matter what the scene is, if it's under the same light as the meter it will be exposed correctly, no guessing or compensation needed. One instant reading and it's locked in. There are many benefits to this, one of them being I need no test shots. I can simply fill an entire card with only perfect exposures, never needing to guess and delete, which saves me time and storage, especially while on the road.
I also use a hand-held when possible during weddings and portrait sessions. Whenever I have time to use the meter and whenever I feel the camera's meter will be too fiddly, I use the Sekonic. This is also because I like to shoot in manual for consistency. For example, when you shoot 20 different groups during formals, you don't need to change flash or ambient exposure each time. You meter it once, and then the shot is the same every time, regardless of what people are wearing. I use the Sekonic at most points throughout a wedding. The other most used alternative for me is spot, and then matrix. I don't need the hand-held for dances because I simply shoot in manual exposure and let the flash do its thing.
