Copy and Duplicate are doing just about the same thing, Although Duplicate SOP would yield a faster result as it has less tasks to go through. The Duplicate SOP is probably more similar to instancing :?: (I don't think it's true instancing, tho). The Copy SOP does literal copies of the object.
The power of the Copy SOP lies in its ability to do stamping so that you can get completely unrelated geometry copied to its template. This is a very powerful feature, though a bit slow.
If you're going to just do straight on copying (duplication), I'd suggest using Duplicate SOP as you don't need any complicated operations. When you start needing to copy to template or perform copy-stamping operation, then Copy SOP will make it much easier.
Hope that helped. A PS: DOn't quote me on what I just said.
If you want to make copies of your geometry, duplicate sop will do just fine. If you want to make duplicates of your geometry and then transform each one seperately, use multiple transforms from your original geometry and use the merge sop to merge the transforms together, then you'll have a number of transform sops you can adjust afterward to place your pieces.
The Copy SOP is a beautiful thing once you learn how to use it. If you wanted to make 100 rocks but you want to have each rock be a different shape, use the Copy SOP. Copy SOP allows you to modify any of your geometry attributes for each instance of the copy. It also allows you to use a template as input. So if you wanted to copy geometry to particles, or to any points, you could do it with the copy SOP.
It is hard to get your head around what the copy sop does at first because a person coming from Maya or XSI will not believe what it does is possible. It takes your source geometry and then, for each copy, goes back up through your entire network before the copy and looks for the param() functions you've added. It then replaces the value for each param() function based on an expression you set in the copy. In other words, for each copy you will get a different resulting geometry if you turn stamping on. I'm sure you could find a tutorial on this somewhere… it also allows you to lookup attributes on your template and use those to trigger deformations.
Good luck! Feel free to ask for more detail if you're interested…
This will introduce you to the basics and you can go from there. Houdini is one of the few packages where you could easily make a snowflake and have it actually be unique each time it's copied, just like real snowflakes. Welcome to Houdini!
ops: asking this:
