I’ve heard some people (bartenders even) describe beer served out of a firkin or through a hand pump as “warm, flat beer”. I think there is a lot more to it than that.
Beer that is served in firkins is naturally conditioned, means that the CO2 in the beer comes from the yeast through fermentation and is not added later like in most kegged beer. This tends to give the beer a softer mouthfeel. It does lead to beer that is a little less carbonated that kegged beer, which is why we prefer to only put certain styles in firkins.
Firkin beer is also served a bit warmer than kegged beer, for certain very hoppy or dry beers, or ones that are not complex, this can lead to a flat, bland flavor. we prefer to put our malty beers like Foul Weather Jack or Transcontinental into firkins for this reason. As the beer warms up, the flavors of the malts really come out. You can end up with a very complex drinking experience for that glass of beer.
It is very trendy to put IPA on a hand pump, but if you are going to try this style of beer then I do recommend something with more malt to it.
If you are wondering where to get beer in a firkin, I can highly recommend aint Benjamin’s Taproom. We always have one beer on our handpump and sometimes a second firkin being served on our bar.