The rhetoric is similar in that both speak of the safety of the hall and of the comfort derived from the gathering of thanes and warriors together. "The Sparrow" uses metaphor while Beowulf employs allegory. While the one is prose and the other poetry, there is a similarity in the use of imagery that marks the hall as a place of refuge and safety in an uncertain world.
The Sparrow in the Hall
the banquetinghall where you are sitting at dinner on a winter's day with your thegns and counselors. In the midst there is a comforting fire to warm the hall; outside, the storms of winter rain or snow are raging.
many a mead-cup the mighty-in-spirit,
kinsmen who sat in the sumptuous hall,
Hrothgar and Hrothulf. Heorot now
was filled with friends; the folk of Scyldings
ne’er yet had tried the traitor’s deed.
There is a definite sense in which both of these texts are allegorical and concern key Christian narratives such as the battle between good and evil and also how we live our lives in this world with respect to the afterlife that Christians believe we can expect after our death. The rhetoric then becomes a thinly-veiled Christian allegory as these topics are discussed and presented to us.
Aren't they both saying that human life is fleeting and impermanent? To me, they are both meant to make us understand that what we do here in the world will not have a permanent physical impact. We will fly through life without leaving much evidence of our passing. The only thing that we can do to be important and for our lives to have meaning is to, like Beowulf, sacrifice ourselves for others and leave an intangible mark on the world.