Your left. Pick one at random. As has been suggested, pick the cheapest.
Unless you know of a reason to choose another one, or you have been advised that your application needs something special, then there's really nothing else to go on.
If you're building a lot or if it is really expensive, make a prototype and test it. Or hire an engineer. Or both.
There may be dozens of things which may be important, and unless someone knows all (or most) of the details, it may be really hard to make a determination.
As an example, how often is the relay switched, under what load, at what temperatures, and what reliability is required? You've mentioned the board is in a dusty and humid environment. What sort of dust, how humid, is it subject to rapid temperature changes, or instances where you could get condensation? Are you considering a conformal coating, or even potting? How is maintenance to be carried out? Does the device need to pass any safety standards, CE Mark, ROHS, etc? How is the device to be constructed, and do the required parts exist in a packaging suitable for automatic insertion? What stage in the lifecycle is the component? Is there a second source? How available is it (is it in the quantity you require)? Is the supply chain reliable and secure? What is the expected service lifetime of the device? Are there different relays used where a single relay type can reduce the BOM or allow better quantity pricing? Is a relay actually required? What about it's weight? Or maybe vibration resistance?
That's just a few off the top of my head. I don't know what's relevant to you, or what other things may need consideration.
