I had meant to take on something a bit less dry today, but here I am again on the scintillating subject of law firm mergers structured with Swiss vereins, or, if you strip away the jargon, unions that maintain separate profit pools. Thank you, Norton Rose.

The first observation to make regarding the debate on the City firm's tie-up with Canada's Ogilvy Renault and South Africa's Deneys Reitz is how polarised the arguments are on both sides. Indeed, the same points have been deployed with the rash of other deals that have fallen short of full financial integration.

Critics say anything but a single profit pool is an unacceptable fudge, while supporters – of who the most vocal tend to be the managing partners doing the deals – say sharing profits is an irrelevance and start talking about client service in the hope the interviewer will lose interest. (To be fair I didn't entirely understand what K&L Gates' Peter Kalis was talking about with regards to Noah's Ark, but I'm fairly certain I didn't agree with it).

Yet taken to extremes both positions are tough to sustain. Multi-profit centre unions are neither good nor bad – they are a compromise to be made because you think it's worth it. More than that, Swiss verein-structured mergers are a tool that you can pick for a job. As a tool they can be used intelligently or dumbly, and will be appropriate for some users but not others. In essence, the model has an upside and a downside. So the question isn't absolute, it is whether the pros of these deal structures outweigh the cons.

And the downsides are obvious and substantive. Compared to total integration, you end up with a weaker system to bind the partnership together via shared ownership and alignment of incentives (though that point only really holds with lockstep-based firms). There is also more potential for ambiguity regarding firmwide management and a danger that the two sides will behave like separate businesses parked together. These factors could easily come to damage effective decision-making or even make it difficult to enforce firmwide standards.

Some have even argued that clients will have a problem with it. Well, if Slaughter and May can pull off selling something as amorphous and clunkily-named as 'best friends', I kinda doubt that. These deals have unified brands and brand goes a long, long way.

Past that, clients will have a problem if the service isn't good enough – they aren't greatly focused on the internal workings of law firms (with the exception of the crucial issue of complaining about what junior associates are paid). But criticism of the model that largely assumes that these potential pitfalls will definitely be, well, fallen into, is built on shaky ground. And remember the same integration problems routinely occur in deals that fully accord to the one-firm mantra – it takes more than a profit centre to bind a business together.

Now let's consider the upsides of the model. It makes integration issues far easier in the short-term. If you're doing a US/UK merger it manages the huge problem of different accounting models and it creates a defined period during which firms can evolve towards parity and full integration.

But the biggest upside is that it lets you get deals over the line that you wouldn't otherwise. That's not theoretical. The siren call of transatlantic mergers has been sounding for years, and what have we had to show for it? A troubled takeover of Rogers & Wells and a series of US takeovers in the City mid-market. But mergers of equals? The game-changers? Nada. Zilch. Bring in multi-polar structures and the deals start flowing.

So while I'd agree that multi-partnership deals have substantial drawbacks, I just reject the idea that in all cases those drawbacks are enough to outweigh the benefits. Does anyone seriously think Hammonds would better off solo or that Lovells shouldn't have bothered? What about the opportunity costs of going for the unified profit pool and repeatedly failing? That's basically what has happened for the last 15 years. Culturally, I don't think the model has much in it for the magic circle – the concept just goes too much against their grain