Recommendation for automated test suite package structure for Selenium testing across multiple broswers

So, I could use a recommendation or two on what makes the most sense on how to structure my automated test package (it's java based using Selenium 2.4.5).

I've thought of two main options:

root test dir -> browser dir -> test dir -> test class in java

or

root test dir -> test dir -> browser dir -> test class in java

I just haven't really experimented enough to know if it's more useful to be able to run the tests based off browser or the kind of tests. For example I could see the benefit of running all IE tests to verify something, but I can also see the validity of running all of the 'login' or 'sign up' based tests so I was hoping someone who has actually implemented and uses this more could give me an idea on what works for them.

Ultimate Goal: Have build variants setup to run against several different environments (dev, integration, staging, and production) and with several different browser options (chrome, firefox, ie, opera, safari, or all) when a commit is pushed and Jenkins job finishes deployment.