Why is butyl iodide preferred over butyl chloride in a williamson ether synthesis?

In Williamson ether synthesis, the reaction begins when the hydrogen from the alcohol's hydroxyl group contacts the halogen ion. Since the iodide ion is larger than the chloride ion, there is a larger chance of collision between it and the hydrogen atom, so butyl iodide is preferred over butyl chloride.

Also, Williamson synthesis is carried out at relatively high temperatures, around 50ºC-100º C. Ethyl iodide has a boiling point of 72.2ºC, so it will be in the liquid phase. Ethyl chloride has a boiling point of 12.3ºC so it will be in the gaseous phase, which is undesirable for this.