I would say it depends on your style of trading and how comfortable you feel in each type of trading. Some guys prefer to scalp the market and take profit from small price variations. Those trades could take like 1min. Some prefer to take a medium approach, and actually try to spot a trend in the price, and leave the trade open for a while, others take a long approach and it's more like an investment, and the trade stays open for days. I usually try the medium or long approach, because I find scalping to stressing, and I can't do it very well.