As far as stats on each discs, they're pretty close to the same. I've thrown both (150z class Flick, Z-Flick, and Champion Firebird) and both of them throw well into a headwind.
My big question is if you're going to throw these discs predominantly sidearm or backhand. Both of these discs are a major favorite among those that throw sidearm, I've rarely seen people throw this disc consistently backhand.
There is a difference in a Firebird and and an FL (Firebird Long), the FL has a little less fade than the standard Firebird. So if you're looking for something easier to control then maybe the FL. Also, the standard Z-Flick has slightly different stats than the 150z Flick. From my experience the standard Z-Flick would be easier to control in most situations over the 150 class version (especially in the wind). Heavier discs will be more apt to do what you want them to do in the wind.
The firebird in ce plastic was the best disc ever made.
Lately my sidearm has gotten too poweful for it, and it won't come back quick enough and hits the ground, forcing me to use a flick for longer shots. Firebird is insanely accurate backhand.
I don't think I would consider either if you are a "noob". I happen to use both though. I use a 150 class Flick. I use the Flick for spike hyzers and in very strong headwinds. IMO it's a bit longer than the Firebird. I use the FL version of the Firebird, because it's the least stable of the Firebirds. FYI the other to are The FX (most stable) and the Firebird (middle of the pack) . I mainly use the Firebird for dogleg lft holes and for thumbers. Now if I had to choose between the two. I'd have to go with the Firebird. IMO it's the most versitile of the two. If you opt for the Flick. You should consider the 150 class, but that's what works for me. I just didn't care for it in the higher weight class.
I use the flick for a poor attempt at sidearm, the narrow profile helps to clean up my release. Also use it overhand, and occasionally backhand into the wind. If Oddjob played disc, this would be his weapon of choice. It's almost like a blade it's so low profile.
The Firebird is one hell of a disc though. I've got two super flat 11X Firebirds; one worn and a freshie. This is one of the absolutely indispensable discs in my bag. I use it overhand (though that really beats the hell out of an increasingly endangered disc) and backhand. If I could throw it forehand, I'd probably just lose the flick to keep the bag light.
Also, when the Flick gets cold or wet, I have a really hard time getting a decent grip....The Pulse is a slightly more manageable overstable driver, but it's still a wind fighter and it comes in ESP. 1.8 rating vs. the Flick's 2.5
When you find two discs with similar flight characteristics, I think it comes down to how it feels in your hand hand and ultimatly how confident you are in the concistancy of your use of the disc. For me, FIREBIRD!!!! I would not recommend either for a noob nor would a recommend a Whippet-X or Xtreme (to overstable).
I agree with everyone here that neither is good for a beginner. I've been playing a year, and these two are still almost too stable for me. They're pretty much utility discs with specific tasks that I use them for. I'd never step up to a long, open hole and reach for my Firebird for example. However, if you throw overhand, I think that either one is suitable for you.
Neither is a good newbie disc I throw flicks and crushs and used to throw firebirds and like Mark ellis said the crush is a much more comparable disc to the firebird. Just make sure you have a strong forehand before pickin these up