Agreed and if you read the questions posted on the Holley support forums, you can see that these systems are not just plug and play as people might think. You're adding a lot of complexity with new possible problems to pop up just take a good look at the wiring harness you have to add (youtube some installs on classic cars). Yes EFI will run consistently better cold starts and cold running, but if you have a well set up and CLEAN carb you have a system far simpler to maintain IMO, and it will run good enough, for most people. Adding a 4bbl carb is going to add more response above 3500 rpms when the secondaries open up. Is it worth it? That depends on you. I think it is but to each their own. To make it work, you have to replace the 2bbl manifold with a 4bbl manifold, of course a new 4bbl carb, and there may be changes needed to the fuel line and accel linkage. On a Merc to make it easier you can use an Edelbrock carb because they came with Webers after the Q-Jet stopped production and the Weber is similar to the Edelbrock so the OEM linkages would most likely work, as might the fuel lines.
I have a Q-Jet on my little 4.3 and am addicted to the Q-Jet howl as the secondaries open up, so for me yes 4bbl all the way....