Keyword.co.uk and Brand.co.uk are on par domain wise when it comes to ranking for Keyword. No penalty, no additional weight, they're treated equally. Google cannot afford to give weight in this way. If I put a site selling Vodka on Whisky.com, it doesn't make it a good match for someone searching for "Whisky" does it? Of course not.
In terms of link building, if your intention is to rank for "Keyword" then you'll trip filters if your domain is also "Keyword.co.uk". You could push a lot more link weight for your keyword at Brand.co.uk than Keyword.co.uk and if both domains are on par, why would you choose the latter?
In terms of what determines your rank, it's on site content, links and brand metrics. For arguments sake let's say 20% on site content, 50% links and 30% brand metrics (although the brand metrics figure is increasing it's impossible to put a value percentage on it, but it's significant). To get that 30% additional weighting you have to have people talking about your brand, sharing your brand, searching for your brand and specifically clicking through to your website after the search has performed. These are signals that tell Google you're a reputable brand and this is what forms the brand dominated top 10's you see in search. This obviously poses a problem if you chose to use Keyword.co.uk and Google has no way of knowing if the people who put in "Keyword" into their search box want to find your site or are looking for the product/service in general. The same for mentions around the web and on social media. There is no way to differentiate between them.
So all things considered, domains are on par, you can't be as aggressive with your link tactics and you're losing that 30% of total weight because your brand signals/metrics are diluted as a result of your domain choice.
In terms of recall, sure, an EMD in some cases may prove to be more memorable but my point is that you're not going to have the customer base to recall it if you're getting outgunned in the search engines as a result of the above.
As for what people click when they're presented with the results. I think it's obvious that people have preference. Sure a select few may look at the domain. Some look at titles, descriptions and some look for a brand they've used before, regardless of the domain. But again, my point is that you're not going to be there in the first place unless you consider the above. The same goes for the keywords they choose, we all Google things differently. Some search DIY, some search power tools. Some search car rentals, some search hire a car. You have to try and cater to all keywords, all preferences to achieve the maximum total traffic. Not limit yourself to the select few who search for "Keyword" and are a fan of matching domains.
Of course we can all list examples of EMDs that rank, of course there are going to be some but in comparison to strong brands they're a serious minority. They've either so much history that they've become a brand in their own right or they're in a niche that doesn't have any clear cut brands so that the above "30%" doesn't come into the equation.
Goodnight x
