Vray and IBL - does HDRI make a difference?

[tricky]

Is it strictly necessary to use an HDRI in the texture slot of a vray light for image based lighting, or would any panoramic (180degree) sky-type bitmap suffice?

[GLASS-CANVAS]

You can use any map type you like, but HDRIs look the best by some margin

[Morne]

because any panorama has just "flat" colours and no hotspots, and HDRI have hotspots in dynamic range I geuss that acts as "lights" instead of just a half blended environment light

[tricky]

because any panorama has just "flat" colours and no hotspots, and HDRI have hotspots in dynamic range I geuss that acts as "lights" instead of just a half blended environment light

Which of the following is correct, if any!?!

A:-
In the case of a LDR panorama (a normal panoramic bitmap), the maximum brightness of the vray dome light is the value of the vray light multiplied by 1 to 255.
In the case of a HDR, the maximum brightness of the vray dome light is the valuse of the vray light multiplied by 1 to 10000 (or float).
In summary, the LDR-based light can be brighter than the vraylight multiplier, but the HDR-based light can be MUCH brighter than the vraylight multiplier because of its much higher (float) values.

B:-
In the case of a LDR panorama (a normal panoramic bitmap), the maximum brightness of the vray dome light is the value of the vray light multiplied by 1/255 (darkest) to 1/1 (brightest), so the brightness can never exceed the value of the vray light multiplier
In the case of a HDR, the maximum brightness of the vray dome light is the valuse of the vray light multiplied by 1/1 to 1/10000 (or float), so the brightness can never exceed the value of the vray light multiplier
In summary, the brightness of the vraylight will never exceed the vraylight multiplier, but the HDR-based light will exhibit much smoother graduations of lighting than the LDR-based light.