Dear Tandrila,
Books like Morrison Boyd have shown that breaking a C-D bond is 7 times tougher than breaking a C-H bond. These are experimental results.
The stability of the carbocation depends on the hyperconjugation effect in both the compounds. Since, it's harder for (CD3)3C+ to show hyperconjugation than (CH3)3C+ . So the second compound will be more stable than the first one.
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