The trailing SL's are better because they follow the share price. The fixed SL's have to be adjusted manually at regular intervals to avoid you from loosing all your profits. In volitile situations I suggest still to use trailing SL's but with a higher %.
Dilligaff2, your logic makes sense. But the bad news is that stops are an art and not a science. There is no perfect stop loss. I use a 20% trailing on my derivative trades and on straight shares I generally use 5-8% depending on the share that I am in. I will also revert to a lower low on end of day price (when long) as a stop and this is classic trend reversal (Dow Theory).
The point with a stop loss system is two fold. First - you have to have one - without you will go broke. Secondly there is no perfect one that always works 100%. Sometimes you'll be stopped out only to see the stock tear off in you expected direction, but without you. And sometimes you widen it to keep you in a trade but still get stopped out, but at a bigger loss.
You can also look at some TA theories such as average true range (ATR), Elders safe stop (or is it van tharp?).