、。
There is little if any difference between the two.
Literal
Both-parties [possessive-の] between [in-には], even-if exists [concessive-にしても] very-little only difference [subject-が] doesn't-exist.
たとえあるにしても (even if there is) uses たとえ (even if, supposing) + にしても (even granting that). ごくわずかしか~ない (only very little) uses しか + negative for 'only.' A carefully hedged statement minimizing the difference.