It depends on the context. If your OTR is going through a central server or a compromised Tor route, adversary can learn who you are talking to. E.g. Adium OTR plugin sends encrypted messages, but identities of Alice and Bob are in the clear to NSA.

Bitmessage does not do any OTR tricks (I myself do not think OTR is very important), but guarantees anonymous routing probably even better than Tor: every message is routed to everyone randomly without any particular route whatsoever. In addition, protocol can be extended to wrap messages with some random person's key, so you get double-clouded routing.

So, Bitmessage might give you even better tangible privacy over Tor, while not giving any of disputable value of OTR.

PS. Why I think OTR is of little value.

OTR is a trick Alice uses to release signing keys after talking to Bob. Bob can retain the info on his disk and be interrogated, but Alice sort of "proves" that anyone could produce that data, so she's innocent. In other words, OTR is not about hiding any information, but about telling the court that "i was smart, you can't prove it was written by me". Logically OTR makes sense, but without being tested in court (which is not a department of logic) it's worthless. And I believe, when it comes to a trial, your adversaries will have plenty of parallel construction in addition to judge's "common sense" to invalidate any trickery that your might have employed. In other words: if you talked to Bob and his data is taken by NSA, you are doomed, with or without OTR.

EDIT: I meant "deniability" part of OTR. "Perfect forward secrecy" is indeed valuable, but not implemented yet.