In general, small diaphragm pencil mics, unless they have a fair amount of color,and are fairly dark, are pretty useless as vocal mics. The low mass of the diaphragm, which responds so well to the fast transients of instruments, especially percussion, tends to cause the microphone to reveal every annoying detail in a vocalist- lip smacking, wavering, breath noise, and the sloshing sound of a wet tongue, phlegm, the whole nine yards. They are also very prone to popping. Now here, I'm referring to close mic'ing. At a distance, these issues are minimized, and small diaphragm mics are fine for ensemble or choral work, in fact, desirable. Now I've got a pair of Neumann KM184's, which are what those Rode's wish they were, and the last thing on earth I would do is sing into one of them.
Here are a couple of exceptions to the rule- Oktava MC012, because of it's color and darker frequency response, can be a fair vocal mic, but I put 2 pop filters in front of it, and never get closer to it than 12". Another is AKG C2000B, a SD mic in a larger housing, making it look like a LD mic. This reduces the popping, for whatever reason, and it comes out pretty good on vocals, if the singer is good, and is also good on acoustic, drums, and as an overhead. Like the Oktava, it has a fair amount of color, and is a little dark.
In general,
acoustic guitar and vocals present very different needs, but I would rather record guitar with an LD condenser, than vocals with a SD. This is particularly true of SD's that are on the brighter side of the equation, such as MXL603, KM184, and those Rodes. YMMV.-Richie