Wine is art. Asking what fermentation rate to use is the same as asking what color an abstract painting should be.
A cold fermentation will retain a lot of the "fruit" characteristics of the wine. If you compare a dry chardonny (fast fermentation) to, let's say, a German riesling (slow fermentation), you will see the obvious difference.
Most let the level of tannins in the wine be the deciding factor when it comes to fermentation rate. Since most reds have high tannins, most reds are fermented hot. With whites, some have high tannins (like chardonnay) and are fermented hot, while most others (like riesling) have lower levels of tannin and are fermented cold. This is because the "fruit" flavor components do not marry well with higher levels of tannin (or so some think).
Of course, this is just a matter of taste and there are examples out there that go against this "rule of thumb". The best advice I can give is to have a goal in mind, then go for it. You need to decide what kind of flavors you ar going for.
Note: Remember to research the temp tollerences of the yeast you are using. Too cold and you could end up with a stuck fermentation, too hot and you can "burn" your wine.