Which one should I buy?

I don't think too highly of Baibars, epecially because levelling Timur's unit should give the same effect as Baibar's active, minus the extra dmg.

As other players do mention, Baibars comes with a HL and the corresponding rewards. IIRC, Subutai's weapon is in Honor of Quest or Soldier, right? I can argue that getting Baibars makes it easier to get Subutai.

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Timur should be able to hold the fort until Subutai's weapon is unlocked. Heck, El Cid and Narses can be ranged gens as well.
Do you need another ranged gen right now?

Timur can still shred weak enemies with melee support. Narses and/or El Cid, among others. Healers Antonina and Eleanor of Aquitaine, or Theodora can provide some ranged support as well, even though they are much weaker.

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Subutai can take an IAP ranged gen's equipment for the ranged points. It's just that he cannot activate his skill every turn. Unless you really need to keep that output, even an early Subutai can hit hard alongside Subutai.

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All in all, I'm biased against Baibars, and believe that Timur or other earlier gens can hold the fort.
However, Baibars still has value in getting Subutai's equipment.

Or, just get Subutai now and wait for his weapon to drop.

Assuming you have good inf gens, you should have the option convert El Cid or use Narses as spares. Justinian + Theodora have a ranged edge as well.

Otherwise, beef up Timur and you should still do well.
Or, give Subutai someone's weapon and he can still use his AOE. Is there a reason to hesitate with buying Subutai? Even without his equipment, he should still do well.

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Since you believe you can get Baibars' weapon, go ahead. You'll be the first here to try for him on the road to Subutai.
We're not very sure of how much value he'd give since he's just a recent addition.

Subutai can deal around 100-600+ dmg per person (1 main target + 2 adjacent to the target) using his skill when he is optimised well (close to 200 ranged points, not sure if there's a minimum). This ignores Dodge and, more importantly, dmg reducing skills like Iron Wall (or Su Dingfang's skin's active).
That's from the best use of his active. You could give him Charles Martel'a Guardian (I didn't even buy him) or Attila's Bow of Attila. Both improve the user's ranged points, which is necessary for Subutai's active.

Think of Subutai as a gen that does damage over time (exaggerated) and ignores defensive buffs (except for skill points). Of course, you MUST invest in Subutai, even of you don't have his weapon, to make good use.
Meanwhile, Baibars ignores Dodge and deal a strong blow to one enemy every few turns, but could be hindered by Iron Wall.


Note: I don't have Baibars' weapon yet (still planning how to beat Diaster at Mari stage 2) and I almost never use him.
Also, I am very biased in favour of Subutai + Murad because of their actives.

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Additionally, this still assumes that you need to buy a pure ranged gen. Hybrids or hybrids converted to specialise in ranged troops can still perform.
Even non-combat gens, with a slight peak in ranged points, can do the job with the right equipment.

Now that I'm playing Baibars' HL, I seriously doubt that a player at midgame could clear it on Normal.
I base the assumption of being at midgame / late early game on the Honor of Soldier (?) (the one for Subutai's equipment) level.

I'll try Annex Antioch 2 again, but I think that without all Talent (Formation isn't unlocked until near the end of Normal mode, apparently), highly specialised gens, and Drum spam, it's not possible for a F2P player at midgame.

I'm running with my gens that beat Normal mode without Drums and Talent, and they aren't doing so well.

firearms expert + Rapid March + Tactic Master are better than Ranged Tactician or Master Shooter.

MMC + MR + Dragoons with single line formations is the most powerful (dealing the highest damage) combination in the game right now.