what advantages does bitcoin have over the alternative chains?

[qxzn]

I see only two significant advantages:
1. a network-effect monopoly. Almost everyone who's using a cryptocurrency uses bitcoin. Relatively speaking, almost nobody uses an alternate chain.
2. Best exchanges. Mtgox and tradehill trade bitcoins, not solidcoins or tenebrix.

Is there anything else I haven't thought of?

[Phinnaeus Gage]

A larger forum with an established membership base.

[kwukduck]

Security of bitcoin grows with network size. So thats a very important point i think.
Also, try turning the question around, why would you want to use alternatives?

Most alternatives i know of implement some key feature that completely destroys the point bitcoin was invented for.

[beckspace]

traction

[Maged]

A competent development team.

[Are-you-a-wizard?]

A competent development team.

Came to say this.

Bitcoin = Ubuntu
Other-chains = Some new Linux distro some guy just made

And yes I know Ubuntu isn't the best distro at all, especially with regards to security, but it's the mainstream one that 99% of the new linux kiddies use and has a massive user/support base.

[evoorhees]

A competent development team.

+1 

A team that has been working since before Bitcoins became worth anything. They're dedicated and skilled.

The better question is, what advantage does any other chain have over bitcoin? Even the most lauded "advantages" are highly contested, and often boil down to economic theory. None of the alts even come close to Bitcoin.

[Rassah]

Technology support, like clients, transaction processing software, android app, ATMs...

[beckspace]

At this point, bitcoin is the protocol and the protocol is bitcoin, and it's sound!

I don't see another crypto-currency replacing bitcoin. The whole concept would lose confidence forever.

Bitcoin is not perfect, but it is plentiful. Bitcoin may be abandoned not because of another crypto-currency, but by its own fault.