Sheriam on level 14 would have an absolute strength between 170 and 195 ... place her toward the top of that level and she's say a 185

Moiraine at the bottom of level 15 would be about 198 ... maybe about 200

Making her only a little stronger than Sheriam who in turn is a little stronger than say Reanne who is maybe a 180, perhaps not even a noticeable difference between Sheriam and Reanne... but then Myrelle on the next level would be a 167 and "Clearly weaker" with Anaiya and company at 163, thus difficult to be sure who was Stronger in that group.

Verin on level 12 could be anywhere from 130-145, and is clearly much weaker from her interactions with the others. Merana is about the same level as Verin and is far below Kiruna/Bera who are close to Sheriam (Or maybe Myrelle, I'd have to check).

Each level simple has a slightly wider range of power than the lower levels, but on this scale strength is not the range it's based on the 21 levels so the "frequency distribution" is not on Power.

As for my quote...
Does it matter which one said it?

TSR
Playing With Fire

"I am stronger than Moiraine," she told him firmly. "She would be whimpering on the floor, or insensible, if she tried to hold as much as I hold now." It was true, though she had never before rated the Aes Sedai's ability so closely.

Further more we can assume Egwene at this stage is only a little beyond 50% of her potential since one book later we're told that she is stronger than Amys and Melaine combined (unless you believe that Egwene was already this strong, which seems ridiculous) ... which would make her about 2x stronger than Moiraine, meaning Moiraine would burn out long before she held close to what Egwene could.