The arguments are: If you breed long to short, you have 2x as many long legged chicks to deal with. You may be inadvertantly be breeding in other unwanted characteristics (ie longer back). Others say breeding long to short increases the fertility and you end up with more short legged chicks to choose from. Its really a choice you have to make. Look at its other characteristics and see if it measures up in the other aspects. Just because it has short legs, doesn't mean it is show quality, but if it has long legs, it certainly is not. Always keep an eye to the standard and breed towards those characteristics.
PS My little roosters usually show their bright red combs real early, even by three weeks its pretty obvious.