These two can often be confused in blind tasting. In the 2013 GuildSomm podcast, Blind Tasting Series Part 3/3, Matt Stamp MS and Geoff Kruth MS have a good discussion on the similarities and differences between Barolo and Brunello.
Neither wine is deeply coloured and both have a tendency to oxidation. So, at a relatively young age they can have quite broad pale rims with distinct orange tinges. On the nose, both can be quite complex showing dried or sour cherry, balsamic, herbal, floral and savoury notes. Both also are typically bone dry, high in acid, high in alcohol, and high in tannins.
Overall I find the primary fruit aromatics on a Brunello to be much riper, richer and dominant than a Barolo. At the alcohol levels common in Brunello and Barolo, Geoff Kruth MS points out, Sangiovese at that ripeness will have a richness that Nebbiolo doesn’t have. He goes on to say that Barolo will have more of an elegance and lightness to it, despite its high level of tannin and alcohol. Matt Stamp MS says for Brunello the acid always dominates the finish whereas for Barolo it’s the tannins that rule the finish.
Barolo: Paolo Scavino 2011 Monvigliero
Dried cherries, dried herbs, and dried flowers on the nose. The tannins begin on mid palate and build onto finish — it takes a moment or two for them to register but when they do there’s no missing them! Compared to the Brunello the tannins are much finer tighter chalkier and more linear. The acidity is quite firm and tart; however, it’s the tannins that dominate the finish
Brunello: Il Poggione 2011
The aromatics are much riper and richer showing sweeter cherry and red fruits (cranberry, plum) than the Barolo. The tannins are more upfront, you notice them straight away, and build onto the mid palate. The tannins are fine but looser knit and rounder. The acid is also high but is juicy and fresh giving a crisp refreshing finish.