You would like to set up your long diamond suit. Best in my opinion is to lead 4th best diamond — the five of diamonds. Your 10 9 of diamonds is not a good enough sequence.
Leading the 10 should promise the nine as well as the eight or seven. 10 9 8 is a perfect sequence for leading the 10 (top of sequence). 10 9 7 is an almost perfect sequence. From either of those holdings I would lead the 10