This is specifically speaking about GMG characters like Yukino, Wendy, Orga, Rufus, Minerva(possible also Kagura) Sting, Rogue. When you look at their ages in correspondence to characters like Lucy, Laxus, Gray, Erza, Natsu, they are all roughly the same age. Now here is the catch, Team Fairy Tail needed second origin to match up with these guys because of the 7 year time skip, but logically they wouldn't need it since the characters above are the same age as them after the Time-skip Point example:
Yukino is currently 18 years old, she and Lucy are more or less on par BUT Lucy is 18 and needed SO to be close to Yukino's strength. Reason being before the 7 year time-skip, Yukino was only 11 years old, and comparing her Celestial Magic to Lucy's, she is stronger than Pre-Timeskip Lucy who is roughly the same age as current Yukino. Which means if Yukino was able to open 2 gates at once by 18 years old WITHOUT SO, she would be stronger than Lucy since the later needed a 7 year power-up( a 25 year old Lucy in terms of magical ability) to achieve the same feat.
See where I am getting at now?
That means all the battles with Laxus vs. Orga, Gray vs. Rufus and etc have been basically about Laxus and Gray fighting their opponents with power-ups that their enemy wasn't able to have, regardless of the timeskip or not since Orga would have been 16 and Rufus would have been 12 years old, and they would have finally "caught up" to the FT members in age.
Now this also carries onto Natsu and Gajeel vs. Sting and Rogue, which I won't explain since you should get the point by now; same with Erza vs. Minerva and possibly Kagura.
So, what does this mean? Compare The GMG characters above to the PRE-TIMESKIP FT members, since it's a valid comparison in terms of power-ups, time spent training and etc. Of course this doesn't correspond to characters like Jura, Lyon and Bacchus, who were shown to be older than the FT characters after the 7 years, but this is an important fact nontheless.
Now *drum roll* for the final question....Who do you think would have won if it was Pre-Timeskip FT characters vs. the GMG members above? If the FT characters didn't get the power-up they didn't need, it means the GMG characters listed above are naturally more stronger and more skilled than them, even if they lost or were one-shotted. Here are the battles below:
Yukino vs. Pre-Timeskip Lucy= Winner? IMO Yukino.
Chelia vs. Pre-Timeskip Wendy= Winner? IMO Chelia.
Orga vs. Pre-Timeskip Laxus= Winner? IMO it could go either way.
Rufus vs. Pre-Timeskip Gray= Winner? IMO Rufus.
Minerva/Kagura vs. Pre-Timeskip Erza= Winner? IMO Minerva and definitely Kagura.
Sting vs. Pre-Timeskip Natsu= Winner? IMO Sting.
Rogue vs. Pre-Timeskip Gajeel= Winner? IMO Rogue.