I think that you need larger pulls for your 36" drawers. 6" will look tiny, and a drawer that size is also much heavier to open also. Get a good, sturdy 10" pull for it.

IMO pulls should be in pproprtion to the cabinet size and that means sometimes there are many different sizes. I use painters tape to figure out what looks best and also they do not all have to be in one direction , you need to think about them hitting each other. This picture is a good example.

It really depends on the style of your cabinets. 6" is very big for a panel door, but okay for a flush cabinet. If the cabinets are already installed buy samples of each and see how they look.

The rough rule of thumb for kitchen cabinets and drawers is that the pull should be approx. 1/3 the size of the drawer or door. But that's just a general guideline, and of course many people go for a different look with oversized pulls. Regardless, the bottom line is that the pulls should vary in size according to the size of what they are installed on; not be all one size. Why else do pull manufacturers make so many sizes.

A useful trick is to make aluminum foil "pulls" in the different sizes you are considering, and hold them up against your drawers/doors. I cut out pieces of cardboard in the several sizes, and wrapped them in aluminum foil. That visual will be very helpful in making your decisions.

Thank you all for the input. It really helped. I decided to do 9" pulls on my cabinet drawers measuring 24" and 12" pulls on my 36" drawers and 6" pulls on my cabinet drawers measuring 15" and 18". My uppers will also get the 6" pulls. Can't wait until the kitchen is fully done and functional!