What he said!
This is a polarising topic!!!!
People on SUs racing in SCCA series (USA) produce big power and swear by them.
People with triples also make big power and swear by them. Some have strokers (3.0+L engines with long stroke diesel crank) and others with modified engines like mine.
This a good discussion on the topic
https://forums.hybridz.org/topic/27322-weber-dcoe-vs-early-240z-su-carbs/
This is a good read from your BMW buddies
https://e9coupe.com/forum/threads/z...nd-other-lessons-learned-along-the-way.23820/
My 2cents as someone with a worked L28 and sorely tempted by triple OERs from RHDJapan. This is a summary of what I've picked up speaking to many people and spending hours reading up on the topic
DCOEs were designed for racing and definitely flow better, especially at the top end.
People state that SUs are better for low to mid range and better for throttle response coming out of those low gear corners.
I asked the very experienced mechanic at CCK Classics (a garage I would recommend in a heartbeat who RR tuned my engine for the run in period) the question about the drivability of DCOEs and he laughed at me saying if set up correctly they will perform well in all conditions.
It seems that it's a compromise - I.e. To get the lower end you need to use smaller chokes but that defeats the object of better flow at top end. Getting a decent airbox like the one MJP Eastern sells seems to also make a noticeable difference to air velocity at the stacks.
People have reported the DCOEs coughing back over a hot header and setting the car alight. I would contend a decent, well designed heat-shield directing fuel away would solve / minimise that issue.
SUs do go out of tune over time as mine have in 1000 miles but probably my fault.
With proper good quality linkages DCOEs are far less likely to go out.
DCOEs sound and look superb and what every petrol head will look at and instantly regress to being a 4 year old.
If you go that route, make sure you get someone who knows their stuff and has a collection of jets etc to rolling road tune them.
And for balance here's an interesting response I received from Ztherapy who remanufacture the finest SUs for Zs ...
My advice is, take your time, speak to lots of people with them, the old lags with experience of both get the right mods on your engine to make the most of the money you'd spend on them.