In Go:

  func isAnagramOfPalindrome(str string) bool {

    charCounts := map[rune]int{}
    for _, c := range str {
      charCounts[c]++
    }

    numOdd := 0
    for _, count := range charCounts {
      if count%2 == 1 {
        numOdd++
      }
    }
    return numOdd <= 1;
  }

In this case I think I do prefer the latter. I like how I can name the intermediate objects. :)

Also I don't like the practice of groupBy().map(=>_.size()), which hides the performance penalty of creating arrays. I'm sure a better compiler can do better, but I'd have to know the compiler to assume that.