Modern treestands (made of aluminum or various alloys) are usually designed with safety and convenience in mind. But they are also stolen easily.
You set up your hunting location, install your fancy $400 treestand in the nearby tree, you come back a week later and... someone stole it. Or lets pretend you got a super cheap $60 treestand, and someone still stole it.
Another hunter saw your fancy treestand, took a liking to it, and since it is so easy to install and takedown, and transport, they stole it and used it somewhere else.
Old fashioned treestands don't have this problem. You build them with wood, nails, screws, etc and they are literally attached to the tree. "Stealing it" would be a lot of work and thieves are lazy.
You have 7 factors to consider when building a treestand:
- How Hard is it to Steal
#6 is taking care of because you are building it out of wood (usually), and it is attached to the tree at multiple points with nails. The effort of taking it down and rebuilding it just is not worth it for most people. (Especially if the would-be thief finds a fancier treestand elsewhere and decides to steal it instead.)
Wood is durable, but in theory you could also purchase aluminum or other materials that will also be durable. You could even use aluminum siding to make a roof for your treestand, which would keep the rain / snow off of it, increase your comfort, and increase the durability of the wooden bits below.
You will want something that is lightweight to build / transport / install. Again wood and aluminum make sense here. You will want to avoid any materials that are heavy. Large wood logs may be durable, but they are also very heavy and not needed. You are building a treestand, not a log cabin.
Handrails are a good idea for safety. They are also convenient for hanging things on. Your platform should be durable enough that you can jump on it with full gear and there is no worry about it breaking.
Wood and aluminum are relatively cheap. Or even free if you know where to get and recycle materials. The real cost here is the time required to build the treestand and the assumption you are handy with tools. (If you are not handy with tools maybe you should stick to ground blinds.)
With respect to convenience you really want a design that is easy to construct, easy to install / connect to the tree, and doesn't take too much time. A minimalist approach, plus a few safety features, should suffice.
Comfort... sitting in a treestand for hours can get really uncomfortable. So you want to be able to sit or stand and move around a bit without any worries.
And there are lots of designs to consider. Including freestanding designs that aren't actually attached to trees, or designs where that ladder also doubles as a support structure.
The last one is really minimalist, but takes a long time to make. ;)