Hi Hopinso!
Much depends on your point of view and who you beleive! But like Linus Pauling says 'a molecule is a molecule'and the body does not distiguish between the two! Hypoascorbemia (subclinical scurvy or scurvy) is inherent in humans and we must find an outside source!
Now you can try to eat fruits and vegetables that are supposedly high in vita C ,but as we all know the mineral and vitamin content of the foods grown in this country have less then half of these substances then they did 30 years ago!
I myself never take it in pill or capsule form or do I take pure ascobic acid unless you take it with alkalizing minerals! Ester C and EmergenC are expensive pill forms of this so I find them of no use, but many manufacture a powder form of mineralized ascorbic acid at a much better price and the powders or crystals allows for the higher effective dosages to be utilized!
I use a product that contains calcium ascorbate, potassium ascorbate, magnesium ascorbate and zinc ascorbate its a fine inexpensive product that cost only 16 dollars for more then a months supply depending on how you are using it!It is sold by the 'life extention foundation' but you must be a member to recieve it at these prices.

~Stridar~

Well certainly the most absorbable/best Vit C is food based, meaning it has all the factors your body expects when it encounters ascorbic acid/ascorbate therefore being more beneficial. That said, it can get quite pricey to take food based vit C supplements at some of the suggested levels (few grams), or ingest lots of vit C fruits and vegetables.
On a balanced diet and healthy body you might only need a few hundred milligrams; but since we are bombarded with toxins every day typically is a good idea to boost that antioxidant to help out on detoxification, specially if toxins have accumulated. It is important to keep in mind on the form of Vit C as you said it may do more harm than good.
Personally I have been taking a food based Vit C with bio "flava flave-noids", and use a couple packets of emergen-c (has 7 different mineral ascorbates) a day for a total of ~3grams a day.
Mike

The ascorbic acid (vitamin C) commonly sold is a very unstable synthetic made from sugars. Back in high school chemistry we took some ascorbic acid crystals and exposed it separately to heat, light, and moisture. Then about 40 minutes later we tested each group for the presence of vitamin C. In each case the synthetic vitamin c was completely destroyed in that short time.

This is one of the reasons I prefer natural forms of vitamin C, such as berries, kiwis, and watercress. The second reason is that vitamin C requires bioflavonoids to work properly. Again these are found in conjunction with natural vitamin C sources such as berries. acerola cherry, rosehips, etc. My personal favorite is amla berry, which is a stronger and more stable form of vitamin C. The polyphenols in the amla berry actually protects the vitamin C in the berry from oxidation. The vitamin C in amla has been found to be about 12 times stronger than synthetic vitamin C sources, and it provides many other benefits such as elevation of superoxide dismutase and protection of the DNA by heavy metals. Other good herbal sources include acerola cherry, rosehips, nettle leaf, and chickweed. Camu camu is a rich source provided it is eaten fresh or dried immediately. Otherwise it is very unstable and will deteriorate rapidly if not dried immediately.

As for Ester C and other ascorbates, these are basically ascorbic acid buffered with alkaline minerals like sodium, calcium, potassium, etc. Still synthetic, still unstable, and still lacking the bioflavonoids unless added separately.

The synthetics are more popular because they are cheaper, not because they are effective. Synthetic C runs about $3 per kilo in small quantities from raw material suppliers. Bought in large quantities by manufacturers the manufacturers can buy ascorbic acid for a fraction of that cost. Amla and many of the other sources I mentioned are considerably more expensive. It is one of those you get what you paid for scenarios.

I personally only use ascorbic acid as an acidifier to increase mineral absorption. Otherwise I use natural sources for actual vitamin C activity.

As for amount, taking mega doses can be a problem for some people. For example my step mother gets urinary tract infections from even small doses of ascorbic acid. And several studies have found that mega doses can cause kidney stones in people with kidney disease as the excess ascorbic acid is broken down in to oxalic acid. Also keep in mind that if you do mega dose for a while it is recommended to slowly wean off the high doses if you ever decide to quit to avoid rebound scurvy.