Hakone or Fuji Five Lakes

Hi, I will go to Tokyo and I plan a day trip for Mount Fuji on 14 April 2013. However, I am not sure if I should go for Hakone or Lake Kawaguchico. Kindly advise.

Mid April can be cherry blossom season around Kawaguchiko. It is one of the nicest things to see the cherry blossoms with Mount Fuji from the Fuji Five Lakes:
http://www.japan-guide.com/blog/sakura10/100414_fujigoko.html
http://www.japan-guide.com/blog/sakura11/110420_fujigoko.html

But depending on the year, it may be a little too early for the blossoms, and depending on visibility, it may not be possible to see the mountain.

Apart from the cherry blossoms, I recommend the Fuji Five Lakes if the sight of Mount Fuji is important to you, because the probability of seeing Mount Fuji from the five lakes is higher than from more distant Hakone. Otherwise, I recommend Hakone because it has the more interesting attractions in my opinion.

Both are really pleasant and interesting to visit.
Personally I'd go for Kawaguchiko. Just as mentioned already you might be lucky and see the cherry blossoms there! With the lake and Mt. Fuji in the background it's such a great scenery!