For most of 2020, it has been a tale of two Sinn Feins. The party in the South has gone from strength to strength with record opinion poll highs that will likely sweep it into government after the next election.
Up north, where it is actually in power, the situation couldn't be more different. In what has been an annus horribilis for the big two in the Executive, the only saving grace for Sinn Fein is that the DUP has had a much worse year.
The buzzwords 'golden circle', 'cosy club', and 'old boys' network' that the Shinners have so successfully employed in the Republic can't be used in Northern Ireland where the party has been part of the Stormont circle/club/network for two decades without shaking it up, let alone overthrowing it.
That isn't the only difference. There is a significant contrast in the talent at the top of the party in both jurisdictions. Sinn Fein's front bench in the Dail dwarfs that on this side of the border.
Mary Lou McDonald's rivals in Leinster House rate her as a formidable political operator. Michelle O'Neill's opponents in the Assembly are in awe of the Sinn Fein machine, but not of the Deputy First Minister.
Her credibility on Covid-19 was shot to bits by Bobby Storey's funeral. Until then, Sinn Fein's response to the pandemic had been impressive. On school closures, workplace regulations and much more, the party had insisted that health and safety trumped all else.
When its northern chairman died in June, principle went out the window. Actually, let's correct that. It wasn't Storey's role in the party which lay behind that rule-breaking send-off. Had Big Bobby's activism been solely in Sinn Fein, events would surely have been conducted within the guidelines. It was his CV in another organisation that caused the regulations to be cast aside.
Yet it's wrong that O'Neill has borne almost all of the opprobrium for the breaches. In that now famous photograph, she is standing to the left of Gerry Adams outside the wake which public health guidelines said shouldn't even have happened.
But who is to Adams' right? Mary Lou McDonald, and a few feet away stands Pearse Doherty. Did the best and brightest in Southern politics not consider how it all would look to a public instructed to obey the very regulations being broken?
Did they not realise that regardless of the double standards involved, this was a crazy move politically which would backfire? Or did they understand all that and - for reasons unique to Sinn Fein - feel they couldn't say, let alone do, anything about it.
Did they collectively have to bite their lip and play their part in this big public charade as the old guard once again flexed their muscles. In the middle of a pandemic, Sinn Fein held a political rally in Milltown Cemetery. Storey wasn't even buried there. The cortege later crossed town and he was cremated at Roselawn.
And while ordinary families were stopped at that cemetery's gates, his alone was allowed up to 30 mourners. How does that image sit with a party which claims to follow in the tradition of James Connolly?
Sinn Fein handled the fallout from the funeral abysmally. It still fails to acknowledge any wrongdoing, insisting that no public health guidelines were breached when footage and photographs belied those claims.
It accused its opponents and the media of politicising the funeral. But responsibility for doing so lay at the party's own door when those with influence in Belfast decided that Storey was a VIP for whom the normal Covid rules did not apply. That stood in stark contrast to the funeral in Derry five weeks later of former SDLP leader, John Hume.
Public confidence in O'Neill plummeted after the funeral fiasco, and it's hard to see how she will win it back. A LucidTalk poll in October showed that more than six in 10 people believe the Deputy First Minister's performance this year has been bad or awful.
Last December's Westminster election was a lousy one for Sinn Fein despite John Finucane's headline win in North Belfast. His success showed the rewards a strong candidate can reap, as much as Elisha McCallion's overwhelming defeat in Foyle indicated the perils of persisting with a poor one.
Sinn Fein's vote was down almost seven percentage points in Northern Ireland in the general election, yet there are no signs that the party has learnt any lessons and replenished its talent pool.
The SDLP team at Stormont is far superior while Sinn Fein's generally fails to fire.
Despite being embroiled in controversy over previous comments on Paul Quinn's murder and a PPE order, Conor Murphy has been the strongest player for his party in the Executive. He looks and sounds like a minister.
John O'Dowd remains Sinn Fein's most capable media performer - there is an authenticity about him. If ministries are based on merit, it is hard to see why he didn't secure one. Colm Gildernew has been an adept and hard-working chair of the Health Committee, and the party should up his public profile.
Mid-Ulster representative Linda Dillon is well respected in the chamber. Of the younger MLAs, Emma Sheerin stands out. But many in the ranks are unremarkable. The democratic centralism that prevails in the party leads to robotic representatives repeating lines that somebody else has written.
Yet northern Sinn Fein has been free of the conflicts evident across the border. The legacy of 'the war' means that young activists here are much more tolerant of the party's iron discipline than their Southern counterparts.
UCD student Christine O'Mahony resigned from Sinn Fein after a colleague, who said he was sent by head office, visited her home to instruct her to delete a critical tweet.
She had advised that TD Brian Stanley apologise for his allegedly homophobic tweet about Leo Varadkar. O'Mahony was told that she wasn't allowed to air her views publicly. She said she wouldn't be silenced as she had joined the party to call out wrong-doing.
From this side of the border, the furore over the incident was almost amusing. The repercussions for someone in 'the republican family' speaking out against a comrade in Northern Ireland have been much graver than a few words relayed at the door.
Sinn Fein's membership has expanded massively in the past decade. In 2010, it had around 6,000 members. By 2016, that figure had doubled to around 12,000, and it's currently believed to be around 15,000.
The new recruits in the South are different to the older republicans who put the team first and toe the party line automatically. They are more independent in their thinking, and more personally ambitious. At times, the two groups seem like oil and water, and the rows that have erupted in the Republic around bullying are often the outworking of both vying for the upper hand.
Despite the tensions that have surfaced, Sinn Fein's mass of enthusiastic young members is the envy of all its rivals across this island.
Currently hitting 32% in the opinion polls, the party's annus mirabilis continues in the South. Some believe that Sinn Fein has plateaued, and its support can't expand any further. But overwhelmingly being the most popular party with young voters coming onto the electoral register gives it room for growth.
Sinn Fein has opted for a super-aggressive approach towards the Fianna Fail/Fine Gael/Green coalition. Its maximalist attacks are hitting the right note with the public. Yet its strident tone carries future risk. Preoccupying the moral high ground to such a degree means that when the party enters government it must live up to the standards it set for others. The electorate won't tolerate a smidgen of deviance.
In Northern Ireland, Sinn Fein has far more wriggle room. The sectarian nature of politics here means that, regardless of how badly the big two in the Executive perform, a sizeable chunk of voters will always opt for the largest party in their own community in order to beat the other lot.
And that gives the Shinners reason to remain upbeat, despite their poor performance this year.