Choosing between RGB LED types
Generally I think you are going about this the correct way. You have to experiment with them and pick the right one for the job. The white balance is a big factor. Many RGB leds are not balanced well. The color temp. is another one. The pros buy from several color temp. bins and mix them up (even the same part number will get binned into different color temps).

Also how well the colors mix varies from LED to LED; you just have to try them.

I can vouch for the following RGB LEG:

Ledtronics SML13RGB2KT

http://www.ledtronics.com/Products/ProductsDetails.aspx?WP=446

You will not be disappointed. Let me know if you need some, I also have a break out PCB for them.