I have a couple of (long term) big inch engine projects. On one of them I am debating whether to go with a 1 x 4 spider intake with a Dom
or go with a tunnel ram with 2 x 750's, or 950's.

With the two fours I get 4 needle & seats, 4 accelerator pumps, 8-corner idle, and I think better cylinder - to - cylinder distribution.

With one big Dominator, everything is "simpler", (or is it ?)

I am speaking in generalities on purpose, this is a street engine and once the fuel curve is pretty close I don't really want/need
to keep adjusting it like a bracket car.

Can 2 fours be dialed in a little closer cylinder to cylinder than a single Dominator ?

Absolutely
Every BB Mopar that I have added more fuel and air through the top end made more power and ran quicker and faster as long as the fuel delivery system would keep up
I'm going to assume you're going to mount the dual 750 Holley sideways so the front carb will feed the front four cylinders and the back carb will feed the back four cylinders so you will need and should tune the idle and transition circuits to feed all 8 cylinders as evenly as possible first Then work on the primary for light part throttle driving under 2500 RPM next and lastly work on the WOT tuning to get all 8 cylinders perfect
Now get to WORK and go faster than you ever have
BTW, I'm getting ready to convert two sets of dual tunnel ram Carbs to E85, one set of 1050 CFM Dominator and another set of 1000 CFM HP 4150 annular carbs, both for 440- heads tunnel ram intakes, one low deck and the other for RB motors and maybe use one set of them later on the B1 NOS motor later

Thanks Cab,
Also I have 8 throttle blades 1 11/16" vs 4 throttle blades at 2".
So more throttle blade area by quite a bit.

I wouldn't consider either of those options for a street engine. For a bracket engine I'd go with a single Dominator.

I'd also invest in a dual AFR system to monitor and get the tune done quicker, whichever way you decide to go

I have 2 of Dom's 650's(1.375 venturi) im told they flow 750+. They are very street tunable and thru my tuning i found square jetted worked best. A bit quicker in response and quicker in my freeway runs from 55 to 120+. They are so streetable you could tell anyone you are injected and they would believe without looking. Mine starts right up with one throttle pump and idles on its own right away. The downside is you will be adding some weight to the car with a t ram and 2 carbs. Don't worry about your streetability, it will be there with 2 of Dom's carbs.

https://youtu.be/28p9FKfxlNU
A video i made to show how these t ram carbs can live on the street and still perform.

You asked about a carb versus two carbs, but with the cost of everything for two carbs, wouldn't it approach or surpass the cost of a EFI individual runner system, like a TR manifold or crossram fitted for injectors? The flexability of the EFI for type of fuel might be worth it. Might be the time to step up to a" do all" electronic system.

Here's another more spirited street vid. I am a truck driver, so i can't blow the tires off at every stop sign or traffic light. You will get the idea thou. Street, no problem.
https://youtu.be/vk0dBRuRtfo

The tunnel ram with two carbs will put drive, out run and generally out perform ANY single 4 intake every time. Anyone who claims otherwise is doing something wrong. Your best money will be spent on carbs from a custom builder. In no particular order is Thumpr carbs (Dom) Lighting Carbs (Mark Whitener) and Baldwin Performance (William). Any one of those three will hook you up. Then you’ll wonder why you weren’t running a TR on the street years ago.

One more, going down the track in the car. https://youtu.be/KGoZVhXEdbw

what i have and enjoy the most is a 2x4 combo, but this is a street engine; probably much milder than what OP has. this system is a very reliable clean burning combo.

Well I certainly would. A ram with two BIG fours is by far the best setup I've used. Probably cleaner and faster than the f.i. setups

Maybe,maybe not It depends on the parts and tuner, correct?

Yes sir and I just wish I would of went with duals years ago. Cold altitude starts can be a pain cos now I'm in Utah at 6400 feet but they drive, run and fly like EFI but of course BETTER and cheaper......NO WIRES needed....

I run 2 1050 Dominators on my 528 Hemi on the street with no issues.