Dylan Thomas and Lord Alfred Tennyson are completely different kinds of poets belonging to different centuries. While Tennyson is a Victorian, Thomas is a 20th century Modernist poet. While Tennyson was a belated Romantic with his tender and languid imagery, tone, mood and melodious cadence,Thomas was quite an anti-Romantic like most of the Modernist poets.
The differences in the figurative languages between these two are thus historically and aesthetically grounded. Tennyson's way of approaching death for example in his collection In Memoriam is a rather emotional and nostalgic elegiac perspective, but if we look at the way Thomas presents the theme of death as premonition in the child's world in Fern Hill, it is more of a harsh, violent and realistic portrayal. Thomas's other famous poem on death is A Refusal to Mourn where he seems to take up a stand against the Romantic emotional effusion and suggests the insufficiency or limitation of language to express elegiac emotion properly.