I voted 'neither' and here's why.
1) The conquest of the RSE: this does not sit well with me at all. One of the most interesting and iconic races reduced to the status of je'pwhi, (sic)this is an utter travesty and I cannot believe that it would actually happen.
My people and I thank you, noble Damar.
Which brings me to:
2) That the KE would have been the dominant military superpower in both Quadrants. How many times have the Klingons wasted ships and resources in their blood feuds and civil wars and constant wars with every power that looks at them funny and yet they still end up either conquering the RSE or threatening the UFP

. It seems that neither the Dominion or the Borg can stop the all mighty Klingons.
It's hard for me to imagine the Klingon Empire being this disciplined and deliberate. I would have said this is something they are just not very good at.
I agree. I have this theory about the Federation, Romulans, and Klingons.
- The Federation doesn't conquer; it 'subverts' most of its adversaries through diplomacy, trade, treaties, and all that good cultural absorption groupthink kind of stuff under the auspices of 'the greater good' and everyone playing nice.
- The Klingons are driven to conquer; they enjoy it, and believe it is the right of the strong to dominate and 'protect' the weak from themselves; in this they are pathetically predictable.
- The Romulans on the other hand are somewhere in between: they don't fight if they can think of a better way, but they do channel their internal rages into it so that when they do, they do so quickly, brutally, and suddenly - so fast that you won't know they were coming; they rely on being enigmatic.
I think that the only reason that the Klingon-Federation war of the 23rd century didn't happen was because the Romulans entered the mix. First they sided with the Klingons, because the Federation was their old enemy. Then that soured, and they played the field as long as they could until the F/K Cold War came to a head with Praxis and allowed a 'forced' peace. This forced peace threatened the Romulans, who, because of various circumstances, ended up withdrawing again.
So then what do we see? This era of detente allows for cultural exchange between the Federation and Klingons, which allows a friendship to form and them to later bond partly because of certain Starfleet officers' direct involvement in Klingon politics and uniting against 'common enemies.' In 'Yesterday's Enterprise' we see a timeline where, without a key step in the Federation/Klingon detente - the sacrifice of the
Enterprise-C - there is war. (Even with Romulan interference.)
My point is that the philosophies of the Federation, Romulan, and even Cardassian (who I haven't totally figured out but I'll leave that to better minds

) are largely reconcilable, but none of them are totally reconcilable with the philosophy of the Klingon Empire.
Natural progression suggests that no matter what friendships and detente occur between them, they will always be forced unless there is a fundamental change in either philosophy.
Failing that, war between the Klingons and Federation (and any allies that tag along

) is largely an inevitability.
My $0.02.
^ I have a theory for the future Klingons, it involves a certain race of shape changing aliens from Beyond The Wormhole!
Now that would be interesting!!
