Depends on what type of fuel injection you're talking about. Bendix style with its low fuel pressure during cranking and idle can sometimes cause issues. With EFI, no issues like that.Questioning the "better starting" comment, especially with a hot engine.
EFI generally improves power over a carb due to superior mixture distribution, even at WOT. Seeing 2-4% more power on the dyno is not uncommon. Some of the 540 intakes are quite poor designs with unequal runner lengths, entry angles and virtually no plenum volume.
EFI throttle bodies don't have the inlet restrictions of carb venturis or Bendix/AFP metering servos so they have lower pressure drop and higher mass flow. This can pick up additional power at high rpms in many cases.