What to put on the window ledge??

I got a new window a while back. I am going to put sheetrock around the interior. The question I have about this is what do I put for the base or ledge of the window. Some carpenter told me to put 1/2 or 3/4 " plywood instead of sheetrock and texture it like the rest with corner bead and such. I am not sure if that is right or would plain old sheetrock be the right way to go? Thanks.

I prefer fir for the window ledge.
But you don't want drywall, any moisture there and it's not going to hold up well.

A table saw is a must for cutting the wood to the right width.

I use oak varnished with a quality exterior varnish to resist moistire and UV on the inside.

Some things you will need to think about before you buy the wood are:

1) the depth of the wood. You do not want to come up too short but can get away with an overhang of a few inches.

2) the width of the wood. Too thick and there is a drop before the window frame.

I use screws to attach the very ends of the sills to the lower header. The drywall on the sides of the opening then covers the screws.

I am going with a contemporary modern look and stained wood just won't work in this situation. I will be mudding the sheetrock and maybe use an orange peel texture. I have some 1/2" pine or fir not sure which that I could use to match the thickness of the sheetrock.