Have long experience here. I started juicing in the early-mid 90's and have done so off and on every since. The off and on more because they are a PITA to clean than anything, so I had to be in the "mood". As suggested, you not only loose the fiber, but some of the nutrients and benefitts in the fiber unless you use it in other ways in your diet. And also as mentioned, to get the most benefit out of a juicer you do need to chew your juice. Benefits are more energy and stamina, a natural preventative of health issues, weight loss and it tastes good. As also said it's best if it is supplemented with other foods.
When I was diagnosed with diabetes last fall I switched gears, changing my diet completely loosly following the so called plate method to beat it in only about 4 months, with the extra benefit of loosing about 35 pounds. All my numbers are still normal, no more diabetes. Then I took the next step a few months ago and switched to a raw diet. I bought a very powerful commercial duty emulsification blender, and it gets used every day 2-3-4 or more times. It starts off as a very powerful juicer that also breaks down the fiber and retains all the nutrients. It will make frozen and cooked foods from raw foods, nut butters and doughs, is a grinder, a food processor, etc all rolled into one. So instead of just juicing, I make fruit and veggie smoothies, sorbets and icecream, hot beverages, soups and stews, use it as a food processor for anything, a dough maker, etc. So the juicer, Cuisinart, crock pot... literally 90% of the other kitchen appliances all remain under the counter unused. And clean up is a breeze by just running some hot water and detergent in it for 10-20-30 seconds, rinse and set aside to drain.
If you go that last route, don't be fooled by those advertised on TV, IE the Ninja, Health Master and such. Not as efficient or well made, they have short very poor BS warranty's and a not so good reputation for customer service. It does cost more up front to get much better, but you'll only have to buy one commercial duty to last you the rest of your life in a home environment. I did the research for weeks, read the blogs and reviews, and the smartest choices were Vitamix, Waring or BlendTec. For my uses I decided on a Vitamix with a smaller container as I live alone that has most of the bells and whistles and endless recipes, bought a half dozen more ice cube trays, and a bunch of high quality containers of various sizes for fruit, veggie and meat storage/freezing that protect the nutrients. Set me back around $750 all together, but you can get into just a blender for less than $400 when deals are running. And it will have up to a 10 year no BS warranty with good reviews on customer service (Vitamix is a family owned business that gets 5 stars for that). I also changed to a farmers market to buy my food - way higher grade, way more selection, and way cheaper than regular food chains.
FWIW