You could write novels about each.
Very very basic thoughts, though, are...
Medium bodied. Clay earth notes. Reminiscent of medium-colored fruits. Often spicy. Good with grilled meats, particularly beef and veal.
My favorite producers:
Livio Sassetti (Pertimali)
The wines are best with some age on them, but many drink very well young, too.
Next to Cote-Rotie (and perhaps Hermitage) these are my favorite wines in the world. Frightfully expensive, but often worth it. Like with Brunello, there are both new world and old-world syled producers. My preferences tend toward the producers in the center or more close to the new world, but I am also not hugely experienced with properly aged old world styled producers.
In general, Barolo is like a more structured, more tannic, slightly more powerful, dark Pinot Noir. There is often red earth, and flowers on the nose. The fruits are usually medium to medium-dark and the wine is more powerful than its weight in the mouth would generally lead you to presume. It goes well with a variety of meats (and cheeses). But, to me, braised or roasted veal, lamb, or pork is a sublime pairing.
For value I like:
Cavalotto Bricco Boschis
Silvio Grasso Bricco Luciani
Albino Rocca Brich Ronchi (Barbaresco)
Clerico is a favorite producer of mine, often slightly more reasonably priced.
My favorite producers are:
La Spinetta (1 Barolo, 3 Barbarescos)
I also love Gaja (no longer identified as Barolo or Barbaresco)
More old world styled producers would include Aldo and Giacomo Conterno.
Another astounding producer is Giacosa, cannot really say if he is New World or old world, as I've not had his best stuff.