"Which is more challenging: internal intra-team negotiation or external client, vendor or partner negotiation?"

Thanks

let us say it is not internal intra- team at all

BUT we could say  external client.

I would say both are equal because you are still negotiating.  Internally it might be easier if you are the boss and you are dominenet. 

I think in general, dealing with a human is challenging as it is. You need to get to know the person, his needs, his wants, his aspirations and the outcome he is expecting from that negotiation. 

Intetnally, the negotiation is being conducted between members of a team. Members that have been working together, that knows each other to a certain point, that are working together on the same general goals. An internal negotiation is going to be about percks or benefits that your employee is tying his performance to possibly a raise , a promotion or even time for vacation.

An external client is a lot harder. You need to impress the client and offer him what he only ''wants'' for him to seal the deal. A client doesnt care about your goals or how you run your department, he only cares about his desired outcome no matter what is going on within your company. It is your job to do so and what you are negotiating is the product that your company sells.

External negotiations are more challanging as here you are dealing with some party for whom his viewpoints are vital based upon his company culture & ethics to which he will abide by always.Drifting the external party to take your way or creating a win win scenario is sometimes futile .In the contrary intra team negotiation is comparatively easy as you always have the support of management if issues prevail.Also people know each other so they adapt accordingly to realise the motive.

Thank you for the invitation to chare my view.

Every negotiation can be tricky even if it is a brain storming with colleagues trying to reach a collective decision and or a very tough negotiation with a client.

In both cases the purpose is to reach a mutual acceptance of either a strategy or a business proposal that can benefit both parts.

Always the interaction with human beings is challenging and needs focus and complete consciousness plus cold blood to avoid any problems. 

Thanks and very interesting question....

Extra client is more challenging and not intra-team.

more challenging beacause of the desired outcome of the extra client and no focus on the goals of the other party.