depends on what you want it to do
Carb spacers are really just tuning tools for when your manifold/carb combo is lacking
Open spacers mostly just act as extra plenum area. This can increase high rpm performance especially when you have too small a carb and plenum on your setup. With a small carb the fuel ends up slamming onto the manifold floor at high air speeds and your fuel distribution goes to hell. The downside is that you lose vacuum signal because signal is dampened by the larger plenum.
The four hole spacers do just about the opposite, they are more for building more responsiveness if you have a soggy setup. i.e. too big of a carb. They increase the signal to the venturi which increases the speed at which the fuel and air fills the plenum. Youll likely need less pump shot with a four hole spacer.
For racing purposes I dont think you'd likely use a 4 hole spacer if you arent having trouble getting out of the hole.
The open spacers are more useful for this purpose, most single plane manifolds have too small of a plenum as it is because height considerations and the fact that its always easier to add a spacer than remove manifold height. Take for example the victor jr where you have the short version and the tall version with the spacer built in. I hever see race cars with the short version that arent using any kind of spacer. I think the rule of thumb is that the plenum should be like 1.5 times the volume of the displacement of the engine.
If you just want more response daily driving then the 4 hole would be something you could try.