Belt just around 60 degrees of latitude is usually an optimal zone for habitation on a human-habitable planet. Because of the rotation of a planet this zone usually displays moderate temperatures and high precipitation (though there are no rains on Arrakis in the normal sense, it would still apply somewhat to what's called el-sayal - rain of dust, which often brings moisture to the ground).
What's more, a planetary weather patterns usually are not as extreme as in other zones there. Also, a polar region is usually high-pressure zone, which means that atmospheric circulation is usually from a polar region towards 60 deg latitude. Translating that into Arakkian terms, this means that winds there will be colder and will carry moisture from polar caps.
In addition to those, rather general planetary weather pattern facts, there are Arrakis-specific ones, like the Shield Wall and other rock formations - the former is a protection from the powerful storms and the latter is a protection against worms.
And last, but not least, is the orbital mechanics. The closer to the equator the better, but obviously Arrakis makes that impossible and I think irrespective of the tech level, fuel consumption would always be a part of economic calculation (be it up or down the gravity well). And obviously, whole infrastructure needs to be protected from both winds and worms, too, which makes it rather obvious which location is best.