hot comb

Hair of any length looks better when it hasn't been damaged from excessive heat and chemical processing.  And avoiding these damaging processes will allow your hair to get longer, since the ends won't be breaking off.

I don't know anything about hot combs, and likely most of us on this board don't as we tend to avoid putting any kind of heat on our hair or harsh chemicals. 

It may make your hair look longer to have it straight as opposed to curly, but the damage you will get is probably going to keep it from growing in the future, because it will break off easier.  So, if you want it a little longer immediately, doing that may give you some instant gratification, but for the long term, you will likely only be setting yourself back, and lose growth that you could have kept.  Your choice.