I prefer the exponential since it gives more weight to recent actioin. I use moving averages as points of support and resistance and for signs of strength. The signs of strength come from the time spent either above or below the moving average.
Both can be very useful, ema and sma. There are occasionally significant volumes traded around these levels as they are used as a point of entry, re-entry, or short covering, sometimes. The more times a stocks crossed a widely used ma like the 50 day, let's say in a one month period, the less useful it will be for the time.