ProPublica is OK but falling from grace as it leans harder into manipulating heartstrings.
Both are notoriously, extremely biased on all kinds of topics, for example Brexit/the EU. The Financial Times actually flies the EU flag above its offices: rather hard to get a clearer statement of bias than that.
That's a strong claim without evidence.
I'm not sure how you'd prove this rigorously though. Just look at other comments in this thread. One commenter observes he never saw a pro-Brexit op-ed in the FT, ever. They're always anti.
The FT and Economist are both focused on economic issues. I don't think you can expect them to campaign for a cause that is (by the admission of its supporters) going to damage the economy. They do consider the positive economic outcomes and possibilities of Brexit within their reporting, but there just aren't many compared to the negative ones. I don't think that's biased, it's fact, and it's fact that is agreed upon by both sides of the debate.
The idea that Brexit will harm the economy is:
1. Highly controversial to begin with. Plenty of Leave campaigners and voters were motivated by a belief that the EU is sclerotic and adopts many anti-growth economic policies that could be reversed or ignored once out. The idea it's economically harmful is not at all agreed on by both sides, but if you read the FT you can be forgiven for having a highly one-sided view on this!
2. Discredited. The whole population was told even just voting to leave would cause a huge recession. In fact the economy grew. Economists quite clearly cannot predict the effects of Brexit because they tried already and were as wrong as wrong can be.
Even Paul Krugman admitted that the stated beliefs of economists on Brexit were "dubious" and "motivated reasoning" ... of course he only admitted this after the vote was in:
https://krugman.blogs.nytimes.com/2015/08/02/freshwaters-wro...
What we’re hearing overwhelmingly from economists is the claim that it will also have severe short-run adverse impacts. And that claim seems dubious. Or maybe more to the point, it’s a claim that doesn’t follow in any clear way from standard macroeconomics — but it’s being presented as if it does. And I worry that what we’re seeing is a case of motivated reasoning, which could end up damaging economists’ credibility.
At this point, reporting on what economists think is about as useful as reporting on what epidemiologists think. They all disagree on everything all the time, so it's a way for the journalists to speak through their chosen 'experts'.
Both papers do provide quite good coverage of particular economic topics, framed by their editorial perspective. But if your understanding of Brexit or Trump (or anything politically contentious) comes only from the FT, you are setting yourself up for a huge surprise.