と言っても vs とは言え .
Apparently they mean the same thing (although, that being said) and yet there are cases when only one of them can be used. For example: 梅雨とはいえ、これほど雨が続くのも珍しい。
The subtle difference between the two expressions is that とはいっても sounds a bit more emphatic about providing evidence that appears contrary to the sentence that precedes it. For example, when you say
The latter sounds a bit more emphatic. I am sure these are not the most effective ways to translate them, but you see a subtle difference in the connotations when I translate as follows:
The former sounds more neutral whereas the latter sounds more emphatic.