The answer is yes the 4/8 CPU will perform better than a 4/4 CPU.
Normally In the system 2 to 3 thousands threads will be running continuously serving different system applications, and user defined applications. so definitely a CPU having four cores and 8 logical thread will execute 8 threads concurrently.
While I was working in a project I have tested my app on 2 threaded system. I have divided my task into 2 threads and executed them concurrently. I have seen that the performance has increased twice but when again I divided it into more than 2 threads I got the same performance as my system is only having 2cores/2thread CPU. when I executed the task dividing it into 4 threads on other core i3 CPU which is having 2cores/4threads I got the performance increase of 4x. but when I increased the threads then again the same performance as previous.
What if its for running 4 single threaded apps? And what if its for running 8 single threaded apps?
So as I have explained above the you might have got the answer. If its for running 4 threaded apps both will give same performance.
but for 8 threaded apps the second one will give exactly double performance.