Could Adam Idah win more caps for Ireland than Troy Parrott?
It's a debate that may overlap with the preferred strategy of the senior team over the next decade.
Parrott is undoubtedly the highest profile member of Ireland's new generation, the Dubliner whose progress has commanded significant interest on account of reports of how he is regarded at Spurs. The pre-season reports at Millwall were glowing too.
In the Stephen Kenny era, however, it would not be a huge surprise if Corkman Idah had more security about his standing within the group.
The Irish careers of the duo are destined to be interlinked, and possibly their club careers too given they both represented by the same agency and will always be aware of what the other is doing.
Idah is a year older than Parrott, yet the prodigious ability of the latter resulted in his promotion at underage level so they quickly became teammates.
When that Irish U-17 side were cruelly robbed in a penalty shoot-out farce against Holland in the European Championships, Idah was leading the line with Parrott operating in a slightly more withdrawn role as the playmaker.
The duo made a cameo appearance in the U-19 bracket before new U-21 boss Kenny bumped them up into his dressing-room.
Parrott's burgeoning reputation resulted in Mick McCarthy extending the senior invitation first, but injury has prevented the Belvedere product from travelling to Sofia.
What Kenny confirmed last week was that the Millwall loanee had actually missed out on his original 23 with David McGoldrick's fitness issues opening the door. In other words, Idah was ahead of him in the pecking order.
This wouldn't be a huge shock to regular viewers of Kenny's U-21 side. Similar to the fuss around Michael Obafemi's omission, it comes down to his favoured divisions of responsibilities and the structure of his forward options.
Parrott was an alternative to McGoldrick and the decision to go for Seán Maguire over Obafemi as next in line comes from a similar belief that the Preston player has experience of operating in the centre of a front three or playing just off the man in that role. The Southampton player does not have that.
The constant here is that Kenny wants a speedy number nine capable of operating through the middle on his own, either with the pace to run the channels and stretch the opposition or the hold-up ability that can bring others into play.
This has been a theme of his recent European success with club and country. In 2016, the hard-working and relentless David McMillan was perfect for the challenges faced by his Dundalk side in the Champions League and Europa League.
Kenny seldom operated with a front two and went with Ciarán Kilduff, a taller and more direct option, when McMillan ran out of steam.
At U-21 level, he always deployed a strong-running operator to set the tone up top. Idah was there from the start and was selected for that brief in the Toulon tournament and through the qualifiers.
If he wanted an alternative he turned to Celtic's Jonathan Afolabi, a star of the U-19 side that reached the semi-final of the European Championships.
Parrott, by contrast, tended to operate as either a No 10 or on the left of a front three with the demand to cut inside to provide support to the middle men, also allowing full-backs to overlap.
That's a different job compared to how Spurs have tutored him, as Kenny explained last week. The teenager was the central attacker in his senior debut away at Colchester, albeit in another system.
"Troy is not one for running the channels all day, he is the one to get it into feet and who can look after the ball, protect it and he has good vision and good link-up play," he said.
"He likes to come right into midfield, that's how they've schooled him. That's like Harry Kane at Spurs, where Harry comes right into midfield and players run in behind him. I see Troy as having those sort of characteristics, who can play in a front three, and you can play into him and be a focal point."
But it's apparent that Kenny is excited by Idah's attributes and he might be better suited to the No 9 shirt in the personality of this team.
Shane Long's recall was no surprise because of his pace and his ability to operate with intensity from the front and stretch opposition defences. McGoldrick has developed into an all-rounder.
Aaron Connolly is like Obafemi in the sense that his better games for Brighton have come in a front two, but Kenny used him on the left of a three when he had him at U-21 level and, while he has acknowledged that the Galwegian is improving his skill-set, it's easier to see him figuring as a wide attacker.
With Idah, there's little room for confusion about the deployment.
Kenny has spoken of the College Corinthians product in glowing terms, and the whisper earlier this year was that he would be promoted to the senior squad if he got sufficient first-team experience. A double-figure number of outings off the bench with Norwich was evidently deemed sufficient.
"Adam has all the characteristics of a No 9 although not a No 9 that we have seen with Ireland that I can remember," said Kenny last week.
"That's in that, genuinely, he's got good physical presence. We've always had players with physical presence but were not quick or maybe the other way.
"But Adam is genuinely quick, fast, but also has a physical presence, more of a natural French type of striker in that he's got a tall physique and is quick as well. He has all the attributes but he's still learning.
"Because of his size he could always score goals but when you go up to the senior game, your movement has to be even better in the box. He still has to learn about that."
There's every chance that education will continue on the pitch in Vasil Levski National Stadium at some stage tomorrow night. Expect it to be the first appearance of many under this management.