The pair will clash at a hustings in Perth on Tuesday, but their views on the constitutional question are very similar.
Both oppose another independence referendum and are pushing for more scrutiny of the Scottish Government.
But what policies are relevant to Scotland and what have they said?
The clear frontrunner, the foreign secretary has promised to give Members of the Scottish Parliament (MSPs) special legal protection, allowing them to be more outspoken as they scrutinise decisions made by the devolved government.
Ms Truss’s campaign has also said she would push for a trade deal with India if made prime minister, with the aim of slashing a long-standing 150 per cent tariff on whisky exports.
Speaking this week, she added: “I will never let anyone talk down Scotland’s potential. As a nation we are stronger together and the UK needs Scotland as much as Scotland needs the UK.
“For too long, people in Scotland have been let down by the SNP focusing on constitutional division instead of their priorities. That won’t happen under my watch.”
Her campaign sparked a furious response from the SNP earlier this month when Ms Truss called the First Minister an “attention-seeker” and vowed to ignore her.
Ms Truss has since doubled down on the comments, claiming “some Scots love me, I can tell you that”.
The South West Norfolk MP has made much of her time growing up in Paisley, and called herself a “child of the Union” who loved former prime minister Margaret Thatcher.
She explained: "When I moved to Scotland at the age of four, I was enrolled in the West Primary School in Paisley.
"A few years later, at the time of the 1983 general election, my teacher asked me if I wanted to play the role of Margaret Thatcher in our class equivalent.
"I jumped at the chance, and gave a heartfelt speech at the hustings, but ended up with zero votes. I didn't even vote for myself."
Stressing her Union credentials, Ms Truss has claimed the last vote was “not a generation ago”, and also claimed “if it weren’t for Scots”, the modern Conservative party would not have many of its ideas or legacy.
The former chancellor has promised to make it a requirement for Scotland’s most senior civil servant, the permanent secretary, to attend the public affairs and constitutional affairs (PACAC) select committee annually.
He has also announced measures to make senior civil servants spend at least a year of their career outside Whitehall or in industry, as well as scrapping pay rewards based on the longevity of their service.
Mr Sunak said: “The plans I am announcing will see the Scottish Government properly scrutinised by the UK Parliament, and required to publish consistent data on the delivery of public services so performance and value for money can be assessed against other parts of the UK.”
On the Union, his position has changed, having said in 2017 it "seems hard" to block a second Scottish independence referendum.
Mr Sunak said this month: “There is nothing more Conservative than our precious Union, and everything great that we have achieved we have done so as one family.
"For all of these reasons, my government will do anything and everything to protect, sustain and strengthen it.”
He has also announced proposals to reform a team of advisers within Downing Street known as the "Union Unit".
Mr Sunak has previously been criticised for giving a brief 320-word, two-minute speech in Scotland, and has accused the Scottish Government of “imposing austerity”.