If you are a gamer primarily - reds, if not, go blacks. You can really fly on the blacks once you get used to them.
There's no reason to use reds unless you're physically unable to use blacks. Reds make accidental keypresses more likely because of both their lighter resistance and less steep force gradient. It can be argued as well that their weaker return force is detrimental to rapid keypresses as well as finger positioning.
mmmmmmmm....... this is highly subjective right there... The bulk of an accuracy problem is User-side.. not the tool's problem...
finger positioning.. um...... i'm not sure what you're getting at with this..
Vertical positioning. If one usually keeps his fingers right above the keys using the return force of the switches, there's more likely to be instances where the keys don't fully return the fingers upward, resulting in differing distances between the fingers and actuation points. This would result in throwing the timing of keypresses off and possibly accidental actuations.
ah... ok ic.. um... i haven't thought much about vertical positioning..
Hmmm...... if the bulk of the weight is on your wrist rest/ where u rest ur wrist, then the finger weight is not going to depress a key enough to activate it.. red or black.. wouldn't make a difference.
now, if you use the Hover-positioning technique.. Your biceps would be holding your fingers above the key..
In this hover position.. I don't see how you'd put any rest weight on your fingers, because even with 5 fingers on the board.. there is no way 50g of force prior to actuation times 5 is going to hold up the weight of your hand...