very true. That's why I avoid juicing fruits high on the glycemic index, which are largely tropical fruits. And if I do add some of those to the juicer I limit the portion (small ping pong sized orange as opposed to a large Navel Orange, small apple vs large apple, etc.).
In general I prefer to eat those types of fruits whole as you say to allow the fiber to regulate the sugar. But there are a ton of healthy foods of vibrant colors and flavors that do not have these issues of high sugar like tropical fruits. Also why I think its important to have a good, preferably small, blender in addition to a good juicer. One is not a substitute for the other. Most vegetables can go into the juicer without issue along with some fruits. While when I choose to use the blender is largely for high anti-oxidant fruits, like dark berries, that simply will not work well in a juicer.
As far as simply eating the fruits and vegetables whole to gain the maximum nutritional value, that's where everyone is different. I have a rule when it comes to taking on a new well-being practise that involves an investment/expense of some sort: Basically there is honestly admitting:
1-the things I will do and stick to it.
2- the things I may do.
3- the things I know I will not keep up.
Very very few people in this country are anywhere near chewing and digesting even the minimum amount of fruits and vegetables required for good health.
And they never will change until sickness is upon them, if even then.
Even if you are leaving some nutrition on the table with juicing it's still significantly more than the average person will take in during their lives of eating mostly processed food.
p.s.
This was was all partially inspired by the documentary Sick, Fat and Nearly Dead which is on NetFlix now. An interesting examination of how our American diet has changed in a very short period of time. The principal character manages to bring his weight down to a healthy level from obesity and no longer has to take medication from simply adopting a juicing plan during a cross country road trip. The transformation of this guy was incredible. I'm no advocate of fasting or crash diets or cleansing, etc. but I certainly see the value of supplementing your diet this way.
Trailer
http://www.youtube.com/watch?v=Gv3vEXy_EwU