You can compare hardpoints, loadouts, and quirks all you want, but in the end, in FP anyway, it comes down to Wins and losses.
So lets take a look at the current FP leaderboard:

At first glance you'd think that apart from Jade Falcon, the IS is CURB STOMPING the clans, right?
Lets look closer...
Total Clan wins: 354,553
Total IS wins: 491,977
But wait, the population of IS is higher than clans, so we can't compare 4 v 6 factions...
I can't tell you exactly what the population distribution truly is but what if we just did the top 4 IS factions? (Sorry Liao, Marik)
Total Clan wins: 354,553
Total IS T4 wins: *358,394*
If Clans are so vastly inferior, why are they only short ~ 4k wins? Yes, this is cutting out 2 factions.
Yes, this is assuming that the 4 on each side are roughly the same population.
Compare the Losses now:
Total Clan Losses: 297,491
Total IS T4 Losses: *329,285*
So Clans have in general, won fewer but lost WAAAAAAAAAAAAAAAAAY fewer if you compare the top 4 (and the last 2 IS factions ain't gonna help on this one...)
So whats the WL?
Clan W/L: 354,553/297,491 = 1.19
IS T4 W/L: 358,394/329,285 = 1.09
That's pretty freaking close to balanced if you ask me.
The thing I can't take into account is that IS tends to fight amongst themselves way more than clan...
That would be good to take into account when arguing tech superiority, seeing how IS v IS W/L would cancel out for this exercise...
Did I make sense?