What did you end up getting?! I have a awesome deal on 2019 Madone SLR, mech but I can upgrade to Ul Di2 easily.
BUT…
Venge Pro is taunting me. LOVE the look of it, wouldn’t need to add anything but Quarq and there may be a sale upcoming.
Any insight on your choice you’d like to share?
I ended up with a Venge Pro - I got it with the CLX64s and have since then upgraded it to Dura Ace and an S-Works saddle for a S-Works build (same frameset anyway). Why didnt i get the S-Works to begin with? They didnt have my color 
From what i could see on the aero reviews, there wasnt much separating the Madone vs the Venge. I did like the Viper Red of the Madone - that is, IMO, the hottest bike out there. But in the end, there were 2 deciding factors:
The first (and admittedly minor) differentiator was weight - it doesnt matter so much on a steady state climb, but when dealing with surges, etc it helps. On long climbs, my fat ass gets socially distanced off the back, but for surges and short climbs, i want the most efficient bike i can get.
More importantly, after reading the reviews, the sense i got was that the Madone was a smooth, comfy ride whereas the Venge was a snappier, livelier and more responsive ride. I have a very strong preference for bikes that are snappy: that rocket when you stomp on the pedals, which are agile and where you can feel the bike responding to your input and to the road. Does this make a huge difference in actual speed? Nope. But it does affect my enjoyment of the ride.
I have to say, I am very happy with the ride. It is pretty much exactly what i was looking for, for fast group rides. My first ride on it was the Laguna triathlon last year and i had no issues holding 35kph on the flats on it, despite riding with the flu.
Side note - i ended up buying an R5 frameset as well: i had an Ultegra groupset lying around and some Lizard Skin bar tape i won as a race prize… so getting a bike for it was a logical conclusion. I have to say, for overall riding, i actually prefer the R5 to the Venge. The Venge is stiff, responsive, etc. But the BB stiffness of the R5 is other-wordly. Stomp on the pedals and it is like pushing against a wall. There is absolutely no give whatsoever. And that bike is almost as smooth as my Lynskey without being dull.
Ha, funny…I’ve been on a Felt AR1 which is a nice bike, comfy for an aero bike, light (Di2, Zipp 303), good climber but feel the need for disc brakes and of course something new. BUT, the bike it replaced was a R5. GREAT climber and what a comfortable bike.
I’m in SoCal too, I was going to pick up the Madone in San Diego but the shelter in place has changed that. I still might grab a Venge Pro if I can find a 2019 w/ Di2. I like the Madone…might be a little too compliant but like you said, gorgeous bike.
Stay safe!