Hi William,

As I understand it   --  it's a matter of style or formality of the text being expressed.

I understand "truc" to be very informal and somewhat limited in scope as to meaning.

"Chose" on the other hand has many more meanings and would be expected in less informal speech or text.

Both are used to express "a thing" --  "truc" being the least formal and can be used for just about anything that comes to mind.  A thingy/gadget etc.

Hope this helps.

Jim