Leaves: coloured shapes or textures?

[Breakfast]

This is a bit of an academic question, as I'm not planning to use the information straight away, but I've been wondering about it for a day or two so I thought I'd ask the experts here. Performance-wise, what is likely to be better: a group of coloured and untextured shapes, or a single shape alpha-textured with the same design?

The example I have in mind is leaves on a tree - I have quite often seen this done by having a shape, approximately a sphere, perhaps, textured with a bunch of leaves on a transparent background. Is this faster or slower than creating a similar number of leaves as shapes and just colouring them green rather than texturing them? If so/if not, why?

[DarkwingGT]

I'm no 3D graphics wizard but I'd think the textured route would be faster.  The only reason I say this is lighting and movement.

Say you want wind, then having a bunch of shapes could actually be moved dynamically whereas a texture could not (without looking funny).  Anyhow, just one reason why one would want shapes.

But for lighting, wouldn't that cause a serious drain on realtime shading if you have individual leaves?  I realize you're having them a flat color, but that way they'd look funny as no leaves would cast shadows on each other.  A single texture would be shaded as the object you've applied it to.  I hope I'm not sticking my foot in my mouth though.