There should be no difference in feel from one system to the other.
Since it is likely that you had much of the throttle disassembled, there might be an issue with the way you reassembled it.
I have a Moroso double return spring installed to the bellcrank arm which is mounted to the center tower of the Weber manifold.
I initially had issues with the weight of the tension on the accelerator. I am using the original Pantera throttle cable.
What I discovered was that in that cable assembly, on the carburetor end is a metal tube that is used for the internal spring to ride over.
If that tube gets bent or deformed in any way, it causes increased effort on the accelerator.
I removed the tube from the cable assembly and now have a very light feel to the pedal. I would and have recommended the tube removal to anyone who asks. It likely is the source of the issue in many cases and really is not a necessary or critical component to proper operation. It just causes trouble.
Also in reassembling the throttle arms to the TB's, the linkage must be at 180°, neutral and not over centered.
You do not want to add additional throttle springs if possible. Regardless of if you are using Weber 48 IDA's or EFI TB's, the throttle shafts will wear prematurely if significant spring tension is added to the throttle assembly.