I've found freezing fruit works fantastic. The main reason I started freezing fruit is to save money and to have quality fruit even off season. For example, when cherries are in season, the price is lowest and the quantity and quality is usually highest. So I buy a bunch of cherries, take out the seeds, then bag and freeze them.
The same applies to just about any fruit. However, some fruits, such as bananas, are available cheaply year round, so I never freeze those. The main fruits I freeze are cherries, berries, and mangoes. Basically any fruit where the price fluctuates a lot in the off season I freeze.
I always clean and dry the fruit before freezing. For strawberries, I cut off the green leafy tops. For other berries, you can just freeze them straight. Basically, I do it so that when they come out of the freezer, they are ready to be thawed and blended.
Mangoes are so large that I cut them in chunks. I also peel and take out the seed first. For most other fruits I do not cut in pieces. My blender is a commercial vita-mix and has no problems with anything. I can throw in a whole apple and it obliterates it. Although I have never tried a whole frozen apple:)
I freeze in 1-2 pound bags. I use a simple plastic bag and tie the top in a knot. Then I bag it again. I'm not sure if double bagging helps, but I like to think it does. The longer its frozen the more sealed you want it to be. A vacuum sealer would probably be the better way to go but I have never bothered with it.
I thaw out the frozen bags in the refrigerator when I run out of fruit. When blending, you can use frozen fruit instead of thawing it out, but you typically need to add a lot more juice (or milk) if you do this. I use less juice and more thawed out fruit from the fridge, and then mix in room temperature fruits such as bananas and apples.
As for freezing the smoothie instead of the fruit, I suppose you could do this but it might effect taste and quality more. I suppose it has to do with keeping the fruit as whole as reasonably possible while frozen. After blending its broken down and may not retain its taste as much when frozen. Although I could be wrong but thats my hunch.
If you freeze a fresh fruit, then thaw it out a month later, its still very high quality. I have frozen fresh strawberries for a year and when thawed they still smelled and tasted fantastic.
Also because I mix in non-frozen fruit and juice, I feel its best to freeze the fruit and not the smoothie. I do however, make large smoothies in the morning, then refrigerate in a sealed container and drink half of it for lunch.