I’m thinking about upgrading my wife’s rig from a size 48 2016 Specialized Amira to a PRFour Disc (also size 48) for next season (only one race left this season for her, and she’s been a bit down (emotionally) due to an injury messing with most of her races this year. She’s a duathlete, focusing on sprint distances (I might get her into Oly in 2021, but I’m not holding my breath 
). I’d like to give her as much speed advantage as possible, but was hoping to hear from other ladies riding the QR bikes.
Thanks in advance!
QR bikes are great (as are so many brands out there!)
Be careful not to confuse road bike dimensions with tri bike dimensions: they are apples to oranges. Do not go by height or inseam for proper frame size. She may be a 50cm, she may be a 48cm in QR. Or there may be something really weird about the QR that doesn’t work for her particular needs (do the armpads not go back far enough?) that a different brand would be better. She might even be a 52cm frame.
The aerodynamic benefits of the tri bike surpass the road bike not only in the frame, but that you don’t have a bar/shifters hanging out in the wind. On top of this, the forward-rotated rider position gets their chest down thus reducing frontal area.
If the setup isn’t comfortable, she will be sitting up with hands on the armpads…which would negate all that lovely aerodynamics of the bike.
But really, the most important question is: what color of PR4!?!?!?
Thanks for all the insights; I always forget that there’s not a 1:1 relationship between road bike geometry and tri bike geometry (I don’t even have my own tri bike yet…want to get her sorted first). We have a regular guy we go to for fitting, so when I get her new bike, that’ll be the first place we go. QR has a 30-day guarantee, so I figure that would work out well.
As for color…whatever she wants!! 
Why the QR? Also, I am 5’ 5" and ride a small Cervelo tri bike. I would think a 48 is too small for her.
Good question! We have ZERO tri shops around here (which is DUMB, given the number of events in the area…), so I was excited about the simplicity of ordering a QR bike (as well as the 30-day guarantee). We’d have to travel at least three hours to find anywhere that carries other brands. It’s very frustrating. 
A tri bike is only fast if it can put the rider in the proper position.
You should get her a proper tri bike fit and coordinates and then determine what frame you can put those coordinates on before spending $$$$ on a bike. Alternatively, if she has a really good position on her current bike, measure the coordinates carefully and use Dan’s stack/reach database to figure out which frames might work.
Thanks for that; she’s had a good fit on her road bike, and our fitter is a triathlon specialist, so that’s definitely something we can do!
Determine fit coordinates first and then look at the bikes that can accommodate them.