Which kanji is more standard?

[Tom]

The first example to come to mind is 解ります vs. 分かります. Rikaichan translates both to "to understand," but only one version is listed in my textbook, and Rikaichan displays the 分かります version when you mouse over わかります (hiragana). Is this an arbitrary selection, or is one the preferred kanji? How can I find this out in general?

[Bueller_007]

The first example to come to mind is 解ります vs. 分かります. Rikaichan translates both to "to understand," but only one version is listed in my textbook, and Rikaichan displays the 分かります version when you mouse over わかります (hiragana). Is this an arbitrary selection, or is one the preferred kanji? How can I find this out in general?

Usually written with no kanji or as 分かります.

For a question like that, the easiest way is Google.