Dragon Cohort vs Familiar

[JediMimeTricks]

My character, a beguiler 5/spellthief 1, will be receiving a shadow dragon as an ally soon. I am currently trying to decide between taking the Dragon Cohort or Dragon Familiar feat at level 9. What are the pros and cons for both sides? I am currently leaning towards Dragon Familiar due to simplicity and balance. Has anyone ever played with either of these feats?

[Airanath]

Dragon Cohort is like Leadership, it allows you to select a dragon as your cohort. It faces the same limitations your DM would impose on leadership (do you or your dm control it, are its stats pregen or custom build, etc), other than that, mostly everything is fair. There is a table on draconomicon indicating the maximun age category of the dragon you can attract, with this feat, you treat their ECL for purposes of attracting a Cohort as 3 lower than normal.
Dragon Familiar allows you to select a wyrmling dragon to be your familiar. If the dragon is older, you can't get it, if it ages, you lose it. The benefits is that it receives all the benefits of being a familiar. (Bonus feats, armor enhaces, share spells and all the stuff familiars gain).

Finally, just a reminder, shadow dragons are not listed on either feats, while your DM might allow you to select the shadow dragon for either feat, that is up to him, as written, you can't take said dragon one way or another. As a DM, I would either not allow a Shadow Dragon companion anyway (its energy drain can quickly break the game), or I would make it require higher levels for younger dragons, to balance up the energy drain (better saves, acess to some protection for enemies that are supposed to be prepared).

[Acanous]

Dragon Cohort is what you want here.
Reasoning:
Dragon Familiar's list is exhaustive and level/alignment limited. Dragon Cohort simply reduces the ECL adjustment on a draconic cohort when taking a dragon as your cohort.
There is actually no rule saying you can't have a dragon cohort through NORMAL leadership, it's just the ECL is so high, with so many HD, it's kind of a bad idea. Dragon cohort nullifies some of this, making it a useable option.

So yeah, for a shadow dragon, you want Cohort, not familiar.

[Morph Bark]

Dragon Cohort would allow you to get a normal cohort with a free Half-Dragon template. Very handy.

[JediMimeTricks]

Thanks for the help, I will take the Dragon Cohort feat.

[Airanath]

You will still want to discuss it with your DM, as shadow dragon is not on the list of cohorts on draconomicon.