Almost all of the flavor and complexity of the wine (and its ability to mature and reach its maximum potential) is already inside the bottled when it is sealed, regardless of the type of seal used. The quality of grapes and the wine-making process will mostly determine the ultimate quality the wine reaches when you drink it. Regardless of sealing technique, there is air bottled inside to promote the microbiological development of the wine over time.
And here is where the minor difference between using a good cork and a screw top comes into play. Once sealed with a screw top, no more air can get into the bottle. With cork, there is some additional breathing that goes on (very little as the cork is always moist if stored properly and if not stored properly and the cork goes dry, then too much air gets into the bottle and the wine turns to vinegar). This means that a bottle sealed with cork will mature and be drinkable slightly earlier than the same bottle with a screw top. However, there are other factors that may influence the rate of maturation even more, including the temperature the wine is stored at. The warmer the temperature, the quicker the maturation process. However, most good wines can be drunk over a period of years and you need to occasionally taste a bottle to determine how they develop and when to optimally drink them. By doing so, a very slight rate of maturation difference (which is what you have between a cork and a screw top) makes very little difference, either in determining the quality or the right time to drink the wine.
The big difference in my opinion is that screw tops are extremely consistent from cap to cap and each bottle of the same wine from the same vintage will taste the same - there will be very little difference from one bottle to the next. For the most part, this is a very positive trait and provides for a consistent and pleasant drinking experience with no disappointment! Whereas, cork by its very nature has faults or at least differences in the structure and composition from cork to cork. While estimates vary study to study, significant cork faults can occur in between 3% and 15% of corks made. And sometimes, whole batches of bad corks are produced and sold to wine makers which can ruin an entire vintage of the wines.
I once had two bottles one right after the other in a restaurant of the 2003 Leeuwin Estate Art Series Chardonnay (a great wine BTW!) which I was paying $160 per bottle in the restaurant in 2007. While both bottles were acceptable to drink, most of us at the table could determine the slight difference and the second bottle not being quite the same as the first. Just being slightly different meant we found the second bottle to be less enjoyable than the first (because are taste buds had been set and were expecting the exact same taste). I am assuming both bottles came from the same lot and were stored in exactly the manner, so the only difference between the two bottles was due to slight differences in the cork.
For some more complex and long aging wines, it may be possible the a specific cork variation may allow several bottles of that wine to achieve a presence that is unique and slightly better than the majority of the bottles. This is one small advantage of cork as I see it - that because of the variation of the cork from bottle to bottle that some bottles may be better than average, however it also means that just as many may be slightly worse than average! And if the cork is bad, the bottle may be undrinkable! Therefore, the slight advantage that you may find a few bottles of a particular wine that are slightly better than the rest does not, in my opinion, justify the ongoing use of cork. I believe screw tops provide significant advantages overall, including:
- consistency from bottle to bottle and 'no surprises'
- no wastage due to 'corked' (were the cork is faulty) bottles that have turned to vinegar
- no wastage from bottles that have been stored incorrectly (standing up) and the cork has dried out (even though it was a good cork) and the wine has turned to vinegar
- ease of use and convenience opening bottles
I have a variety of corkscrews and love taking the cork our of a bottle of wine, especially a saturated cork that has been in the bottle for 20 or more years. Getting the cork out successfully is like the thrill of landing a 15 - 20 pound fish on a 6 pound test line! Removing the cork from a bottle is like foreplay before sex - an enjoyable part of the anticipation and build up to drinking the wine. Therefore, I have and will always have bottles in my cellar for the next several decades that have corks for sealing. But I do applaud and agree with the wine makers to switch over to screw tops as the right thing to do - for the wine, the wine maker and the consumer.