Stick shuttle

The legth corresponding to your loom width allows for a comfortable weaving of full width cloth.

For weaving with different weft threads simultanously, you need as many shuttles as you have different weft threads.

If you only use part of the loom width (for weaving a belt, for example) or for certain techniques employing supplementary weft, smaller shuttles come in handy.

My advice:
Stick shuttles work nicely with rigid heddle looms. I suggest not to use boat shuttles, as they are often too thick for the small shed typical for these looms.