This is as an old threat, but let me pontificate to an empty room for the hell of it.
I think all grain tastes better, and I don't really agree with the notion that the reason it only seems that way is due to a better brewer, since ppl get around to all grain when they are experienced. Could be a factor, but my personal anecdote debunks that for me.
I was an extract brewer for a decade, and fairly quickly I put a lot of money and effort into controlling EVERY aspect of my beer to get a quality product. Some examples: I made yeast starters, oxygenated my wort with an oxygen tank and stone, used RO water and created my water profile (ensuring my extract didn't already have minerals added), boiled full volume with a quality brew kettle and propane burner, controlled fermentation temperature in a rigged up chest freezer, ensured my extract NEVER scorched at the bottom of the kettle, sanitized like a NAZI to the point that I annoyed fellow brewers with my analness, used a wort chiller, racked to a secondary, cold crashed, even tried cold filtering, aged my brew (up to 4 years), ensured that my extract was as new as possible, steeped specialty grains, and tried just about every goofy trick under the sun to get extract to taste better (e.g. tried adding at flame out to reduce caramelization, used priming sugar in the recipe to give a dryer finish and cover off flavors, dry hopping, trying exclusively DME since people often say it works better, etc.)
After doing all this, I noticed ONE theme: only my big beers came without the twang. Every single smaller beer I'd make came with that unmistakable, yet indescribable, home brew twang. That weird flavor (almost like wet cardboard and burnt sugar, but not exactly) would present itself to a varying degree in all the light to medium bodied beers I made. Only my imperial IPAs, imperial stouts, big strong ales and barley-wines, etc. would come out so flavorful that the twang was masked. The only problem with that is brewing a huge beer with extract is so dang expensive, and I don't like only making big beers.
When I switched to all grain, I could make small beers all day and never have that twang. Granted I make all grain with all the variables controlled mentioned above, so I'm not saying any amateur can hit all-grain home runs every time. But even when I make mistakes on my all grain, it comes out better. You can seriously sample the wort and notice that it's better. Typically extract wort has a slightly funny flavor, particularly when brewing a smaller beer (often a little astringent, burnt, just off) and I'd always just assume fermentation would take care of it, but it never would. All-grain wort tastes as wort should, smooth as silk and delicious. Try adding it to whiskey sometime, it's awesome.
All grain doesn't have to be an expensive transition either - BIAB is so cheap, and the money you save on ingredients will quickly offset any investments you have to make.