As the new Sunday Times 100 Best Companies lists show, people like working for professional service firms: seven out of the 20 Top Big Companies are consulting or audit firms. In the SME list as well, consultancies are up there with charities and creative companies as being great places to work.

So what, you might say, as someone who buys or uses consultants, you don’t care. Maybe you don’t – but maybe you should.

We all know that it can be incredibly hard to tell consulting firms apart. Not only do they describe themselves in the same terms, but also it’s nigh-on impossible for an outsider to verify what they say. You could argue that the Sunday Times’ list helps do that, but I think it’s important for other reasons. The way an organisation treats its employees is the flip-side of how it treats its customers, and vice versa. Understand one and you understand the other. On this basis, we should look at the Best Companies list for what it tells us about the way these consulting firms treat their clients.

Avail specialises in performance improvement and change management in the public sector. “Like many consulting firms, we’d say we’re open with our clients,” says Martin Wilson, one of the firm’s co-founders, “and that we strike the right balance between being supportive but challenging.” But the difference for Avail is that it’s exactly those characteristics which have earned it a place in the Best Companies list. “We treat our employees with respect and are completely honest with them about every aspect of the company,” he says. “We’re a collaborative organisation that doesn’t tolerate lone heroes.”

Matt Rogan at Lane4, an organisational change and leadership development company, subscribes to the same philosophy: “We have ‘Magic Monday’ sessions in which anyone can ask anything, however challenging, about the business, something that’s mirrored externally in the frank dialogue we have with clients. In times such as these, you’ve got to be prepared to give open and honest feedback, whether you’re speaking to colleagues or clients.”

“We started with the simple premise that unhappy people don’t do good work,” says Clive Hutchison at Cougar Automation, another firm on this list, this time specialising in control systems. He’s a proponent of strengths-based management, the idea that we all perform best when we’re doing things that comes naturally to us. “We change jobs to fit the people, not the other way round,” says Hutchinson, an approach which has seen the company improve its customer satisfaction rating from 40% five years ago to 90% today. Tim Lloyd at the outsourcing advisory firm Alsbridge, which also won a place on the list, agrees: “It’s a virtuous circle. Our clients like working with us because we have people who like working for us.” Alsbridge also featured in the list of the fastest growing companies: “But the Best Companies is more important,” says Lloyd.

The other theme that comes through when you talk to people in the Best Companies list is a sense of belonging. “It’s a bit like a family,” says Holly Maxwell-Bocock at Meteorite, a marketing consultancy. “We’ve a massive kitchen where we can all eat lunch together. Clients come, too: we’ve a big office so they hot-desk here if they’re working in London – and they get to see what we do.”

What that translates into, from a client point of view, is continuity. “We’ve just celebrated our third employee who’s worked here more than 25 years,” says Louise McDonald at global people development specialists, Impact International, “and a third of our staff have worked here for at least ten years. Engaged employees equals engaged clients: we will give our clients a memorable and consistent experience that results in long term business results by doing exactly the same with our own people.”

So the next time you’re planning to hire a consulting firm, why not ask them for the results of their employee satisfaction survey? That will probably tell you more about how satisfied you’re going to be with their work than their proposal.