I build custom made, on site, timber decks, using mostly Balau, a nice strong hardwood with a long straight grain.
There are many types of timber available, but Balau has proved itself to me over the years, being one of the more stable and durable timbers. It is also more readily available, especially the structural timber, than the other hardwoods on the market. I have worked a lot with CCA treated pine, some good pine, some, not so good, but either way it’s like chalk and cheese. Regardless of what anyone might say about pine being slow grown or undergoing special pressure treatments, it’s a softwood and doesn’t handle heavy traffic as well as hardwoods.*
The various Eucalyptus species, like Saligna, are nice hardwoods, but unless carefully sourced and selected, tend to have a lot of disturbance in grain and can act quite eratically outdoors.
I have no problem to work with any type of timber, as long as the planks are reasonable straight and have a bit of length to them.