Isn't it so that more jets and needles (thus more adjustment settings) allowes for preciser tuning?
Yes. More air/fuel circuits can allow better & more precise tuning, but its also more complex and more time consuming and not within everyones grasp. The size, length & shape of the carb's bore / venturi also play an important part in performance in addition to the float circuit and those are things that most people can't tune without the proper equipment & knowledge to do so.
Most of our riding time is typically spent on the needle, which is why the needle length, diameter & taper is vital for performance. If you look at the CRF, YZF & KTM forums where people have bought the James Dean custom tapered needle kits sold here on TT for ~$70, you'll read all kinds of positive comments about those kits and for good reasons. Edelbrock also has a special needle that's precision back-cut to a special taper and you won't find this type of multi-function needle used in the Keihin or Mikuni carbs. In addition to the clicker adjustment on top which raises or lowers the precision back-cut needle and the external accelerator pump adjustment screw, the needle itself can be swapped out for different applications. As with most carbs, the Edelbrock also has an adjustable idle circuit.
My 'guess' is better WOT performance might be obtained from the Edelbrock with the addition of a main jet, but that's only specualtion on my part. If it comes right down to finding a carb that allows an engine to produce the highest peak HP, then I would think the Keihin FCR would be the ticket because its really a very fine product, but peak HP isn't everything in my book and there's more to the definition of performance than just peak HP when I'm looking at aftermarket products. For instance, there's plenty of aftermarket pipes that claim to make more power and people regularly line up to buy these claims to get the most power, but not everyone takes into account the shape of the power curve or the fact that they may be losing power elsewhere to get more peak power. I may not get the most peak HP from the Edelbrock carb when compared to a properly tuned FCR, but its not too far off based on dyno charts I've seen in the past and it offered other important features that were attractive to me. Another interesting thing about the Edelbrock is that its accelerator pump only squirts fuel when you twist the throttle quickly, otherwise it returns the extra fuel to the bowl unlike the Mikuni TM or Keihin FCR where the accelerator pump squirts with every single twist of the wrist. If I'm out for a longer ride in the desert, I try to be concious of this and work the throttle accordingly to conserve fuel, but its hard to be gentle on the throttle due to the grin factor