[LDiCesare]

I wouldn't compare a dragon and a wyrm. They fill different roles in my opinion. Wyrms are pure SCs, expendable, better used with awe and 0 magic path.
Dragons are early expanders, not expected to last long in this role (whereas a magic-less wyrm remains efficient longer) and a good single-bless chassis.
I prefer blue dragons over the rest because an F bless is somewhat limited, while W increases the dragon's defense and is more useful in general (at W9). Nature can be a good bless, but those nations that benefit from it most will likely want an E bless on top (all giants). The bile attack of the green dragon in vanilla is just worthless, whereas the ice breath is useful, if not much.

In my opinion, your pick a dragon because you want to expand fast and benefit from a bless (I got some good results with W9 blue dragons with EA T'ien Ch'i for instance). Once you've built enough armies that your dragon no longer has indies to take out, bring him back to a lab, or a province where you want to push your dominion, and have him forge stuff/research until he is needed for a battle with some army support.