So is it the Leinster of 2009/2013 or a newly-emerging Leinster now? Comparing teams of different eras is fraught with danger so we'll tread wearily ahead of tonight's Guinness PRO14 final showdown with Scarlets.
Indeed, given a gap of just five years, the time principle doesn't really apply.
What I see when I look at Leinster now, on the back of the last decade, is a professional entity built on the principles of the great Liverpool football dynasty of the 80s. From the top down, Leinster Rugby is a well-oiled machine. Chief executive Mick Dawson deserves enormous credit for the organisation that has been developed under his watch.
Of course, he and his professional game board have made mistakes, with the Matt O'Connor saga and how poorly that departure was handled the most glaring. And lest we forget Leo Cullen was given an equally rough ride by so-called Leinster fans when he took up the coaching reins (much like Anthony Foley in Munster) upon his playing retirement.
So what has changed in the interim? Precious little if the truth be told. For me there have been two key factors, one tangible and the other probably not so much.
The underage system and specifically the schools has always been there, without it there would be no professional oval ball code and anyone suggesting otherwise is delusional.
Rugby in the schools continues the heartbeat of the game in Ireland, and in emphasising that I'm not in the slightest underplaying the role of underage rugby in the clubs from minis up.
I would like to think that David Nucifora and those central to the running of the game in Lansdowne Road get the loaded relevance of the schools to the success we are witnessing at provincial and international levels now. We tinker at our peril.
The second major factor, as distinct from change, has been the further development of a much more efficient academy system, whereby the input of key figures - not least Peter Smyth and Dave Fagan, as well as Simon Broughton, Hugh Hogan and Noel McNamara plus Trevor Hogan as overall provincial talent coach - has been immense.
These are guys who understand the underage system, and not just what it takes to make the grade but how best to handle young and emerging talent which, while physically strong, can be emotionally weak.
Given the quantity and quality of talent, the same now as ever it was, it is substantially bridging that cross over that has made for the biggest single difference.
I think it fair to say, too, that, prior to this current year, 2009 represented the pinnacle for Irish Rugby, what with that second ever Grand Slam and Leinster subsequently taking the Heineken Cup followed by Munster lifting the Magners League.
It was a truly great Leinster side that went along the lines - Isa Nacewa; Shane Horgan, Brian O'Driscoll, Gordon D'Arcy, Luke Fitzgerald; Johnny Sexton, Chris Whitaker; Cian Healy, Bernard Jackman, Stan Wright; Leo Cullen, Malcolm O'Kelly; Rocky Elsom, Shane Jennings and Jamie Heaslip. And we're not forgetting Rob Kearney, Eoin Reddan, John Fogarty, Girvan Dempsey or Fergus McFadden to name but a few in reserve at that time.
Over the next four years, Leinster became the dominant force in Europe, with others such as Isaac Boss, Richardt Strauss, Mike Ross, Nathan Hines, Ian Madigan, Sean Cronin, Devin Toner, Kevin McLaughlin, Sean O'Brien and Brad Thorn firmly in the frame.
In truth, it's much too early to compare this current squad with that, but the 'Liverpool way' from times past needs little elaboration through the transitional presence of Healy, Sexton, Nacewa, Toner, O'Brien, Kearney and McFadden on the field, but equally in Cullen (what an incredible rugby record to date), Dempsey and Fogarty off of it.
To that, add Stuart Lancaster and I think it's fair to say that in taking on the much-maligned English head coach post RWC 2015, Dawson pulled off his and Leinster's most impressive piece of work to date.
I say that with the greatest of respect to influential player signings of the quality of Nacewa, Elsom, Thorn, Whitaker, Hines and, of course, the mesmeric Felipe Contepomi.
What Leinster Rugby has in place is a boot room fit for purpose to which the other three provinces must aspire. Munster come closest but have still a fair way to go.
Victory over the Scarlets would make for the greatest season ever. But irrespective of the result, and we dearly hope they win, this young and developing group will be in the mix for medals for many years to come.
And lest any of my Welsh friends think I'm underestimating the reigning champions, then think again.
Irrespective of the result in the Champions Cup, this is a different challenge entirely, most particularly in psychological terms.
I love what Wayne Pivac and Stephen Jones have developed at Llanelli. This is a great Welsh region that plays winning rugby in the right way.
They ate us up (Leinster and Munster) and spat us out on our own patch a year ago and are well capable of doing so again.
But my heart and head says Leinster.
Guinness PRO14 Championship Grand Final
Aviva Stadium,Tonight, 6.00pm