Have been trying to buy an SL7 since 2021 and my LBS just hasn’t had the clout to get one from Specialized in Canada (‘added to the forecast but was not able to be booked’) am now waiting on the SL8 release or whatever is coming from Specialized this summer (maybe this week).
With the release of the O2 VAM was thinking, outside of the world tour, where is the lines roughly for when a aero, all-round or light weight bike make sense? I am aware of the whole 5W less drag makes a greater difference than 1kg of weight loss generally (or something like that) but how much elevation makes it a different bike category more appropriate? My rides/races generally include <1500m of elevation (less than a single grand tour climb in a lot of cases) but how much elevation before you would start looking at an all-rounder rather than a aero bike? In my area the average climbs are 5-8% and 4-10 mins long, have rarely encountered up to 14% and >15mins of sustained climbing.
I wonder how much elevation is required before you lean towards all-rounder like SL7 rather than full aero like S5?
Canyon Ultimate CFR is what you need 
I had the same question two years ago when I was new to cycling. I bought a bike with the best geometry for me. It’s an endurance bike and I overtake a lot of very expensive aero bikes during my rides. 
If you don’t race at the top it doesn’t matter. Your training, fit and nutrition on the bike make a bigger difference than a total of 15 watts at 45km/h (aero frame and aero wheels).
Looks are a different topic however.
The weight difference between aero bikes and lightweight/all-round bikes these days is generally less than 1kg for similar specs. That’s like…a water bottle. Or that burrito you ate for lunch. Don’t sweat those sorts of differences. Buy the one you think looks the best in the coolest paint job at your budget that you can actually purchase.
The difference in drag between aero and all-around frames is starting to shrink. Tour Mag does a lot of aero testing and you can find some results and commentary if you dig through the plethora of posts on the weight weenies thread:
I believe the simpleton pride is the fastest they’ve tested at 199 watts. The S5, SystemSix and Aeroroad are in the 202-205 watt range. The SL7 was 210, the new Propel (which was made to be more like an all-a rounder) was 209 and the new SuperSix was 207. All tests were done with the same or at least similar depth wheels.
One thing to note that I’m sure you know already, is the position trumps frames. So there is a good chance that an all-arounder with 36mm bars is going to be faster than an aero bike with 44mm bars when someone is actually riding it. I say this as (1) all manufacturers seem to spec bars that are too wide and (2) it may be easier and cheaper to get a narrower bar for an all-arounder.
Aim the end get a bike that you will enjoy riding (and looking at) the most
Lots of good advice above. Other factors I’d add (in addition to looks!) that should probably be higher priority than fretting over a few hundred grams of weight or a handful of watts at 40kph:
- fit
- availability. If you haven’t managed to source an SL7 in 2 years of trying you may well not fare any better with the SL8 as and when it comes out!
- local support for warranty, servicing, parts, etc.
- flexibility for swapping out parts if you want shorter cranks, narrower bars, longer stem, etc. E.g. I believe the Aeroad integrated bars are almost impossible to buy on their own, so if that bike doesn’t come close to your fit coordinates out of the box then probably not an option
- livability. E.g. Top model Giant Propel has integrated seat post which might be an issue if you want to travel with it, and comes with hookless wheels which might be an issue if you don’t want to run tubeless
I think there’s loads of good options now that are both light and aero enough that you’re giving up little or nothing in terms of performance on either front and can therefore focus on other things.
Not going to debate the all round vs the aero bike. My last bike was top of the line 25 years ago. It lasted a long time and I loved it. My new bike (SL7) is a great bike and I love it. I expect to get 25 years out of it. Have you asked your LBS if you bought a SL7 from the states would they be willing to assemble it? I had that done but it was inter USA. Shipping was about 100.00 us.
I’ve got nothing to add other than I sit in a similar quandary choosing between the Merida Reacto (aero) and the Merida Scultura (lightweight racing) bikes.
I’d think it would need to be pretty damn hilly, and more importantly steep, to choose an all-rounder over a full aero roadie. You say your climbs are in the 5-8% range, so I wouldn’t consider that steep. You also need to consider your w/kg up those grades - the higher your w/kg, the less weight matters.
The difference in frame weight would be in the 300g range. This is assuming you are equipping both bikes with the same wheels, handlebars and such.
my FTP progress is slowing around 3.9 w/kg, hoping to break 4 w/kg this year, either need to lose 2kg or gain 8 watts or a little of both.
Definitely interested in both of those bikes based on the discussion here the consensus seems to leans towards the 2-5 watt gain with the S5 or System Six though, even if it results in a 1kg penalty.