The difference is how fast the sugar absorbs and the type of sugar. Fruit sugar is mostly fructose and the fibre in fruit will slow down the absorption. Fructose apparently doesn't need insulin to absorb and improves insulin sensitivity, but I've seen contradicting studies (not that I would trust them anyway).
You don't want sugars to absorb fast; that's why simple carbs have a bad name compared to complex carbs (even though both are just sugar). Foods are given a property called the glucose index depending on how fast the sugars absorb. There's several sites which have databases of glucose indexes for foods, which you can search for.
Putting a maximum sugar intake is oversimplifying. You want to avoid any fast sugars/carbs (junk food, like cereal and sweets and cookies). Fruit has fibre to slow down the sugars, and besides, it's got plenty of good stuff in there that you need. So I wouldn't cut the raisins even if I was trying to keep under 48 grams/day and it was putting me over.
Read
this about sugar and insulin. I know it's long but it explains what you want to know about sugar better than anyone could in a short reply. Once you get comfortable with understanding sugar's affects on your body, you should be able to tell if you are eating too much sugar just through self-analysis... read the article, you'll understand then.