the KMS105 will have a slightly tighter pattern than the 104s, but this wouldn't be my main point for deciding which mic to use. The most important thing is that the vocalist has to feel comfortable with the sound of the mic. Regarding "accuracy": I'd associate that with the mids & highs, and both mics are very straightforward there. The bass response is then more for "comfort". Proximity effect will give a distance-dependant bass response anyway, and then it depends on how far away the mic is used, and how warm&comfy the sound is supposed to be, if the 104 or the 104plus is a better choice. The main difference between the two is in the sub-200Hz range. Held at a distance, the 104plus will sound more "natural", at close range I'd mostly prefer the 104 & 105.
Best regards, Martin Schneider / Neumann Mic. Development