Too much frontal area associated with all that Enve tilt hardware, especially if extensions are under the bar. Plus the cable routing on the Enve bar makes the build an absolute nightmare and then the turns in that routing are so tight / sharp that if you're using rim brakes or mech actuated hydros the modulation of your braking is compromised. You also have to consider your preferred bull horn position. The grips are really swept forward compared to other bars and if you have an aggressive position and/or a lot of pad stack and/or short arms you might not like this. I actually do like it because with the under mount setup and normal arms the bullhorn location relative to my pads isn't that crazy. But I know people who hate this aspect of the bar.

I don't have any experience with the Aeria thing but I know it's what I would buy if I could hit my stack on it. I'd need a 54 P4, which I have actually considered buying so I can try this bar. I just can't wrap my head around buying a bike with notoriously poor braking and clearance issues.

Anyways I think the 51 Speed Shop front end at least belongs in the conversation here, as well as the Alpha X, which is surely the most aero. The Culprit bar/stem should probably be considered too -- we don't know enough about it yet though.

The Enve bar and the Zipp bar are both long in the tooth. They are old bars and front end systems and neither of those companies seem to give a shit about updating them or innovating in this space because they would rather focus on products normal people actually buy on which they actually make money (i.e. wheels). I don't know why anyone buys one of those bars with all these better new options hitting the market