Rule #1 of collecting is collect what you enjoy because then it doesn't matter if it ever becomes "worth" something or not.
That said, I think autographs tend to hold their value than cards, with the exception of the old pre-war cards that are very rare and hard to find in good condition. Old cards have value because people didn't save them, didn't slab them in two-inch plastic, etc. They got put in bike spokes, thrown against the wall in games of War, clipped, thumb-tacked and eventually thrown away by mothers whose sons had gone off to college. In the 80s/90s, everyone and their mother was hoarding cards thinking they'd be a suitable replacement for a 401K account. That stuff was massively over-produced and everyone has it.
IMO autographs hold their value much better, though the return on investment might be slow for common signers. Deceased HOFers like Mize, Slaughter, Feller, Kell, etc. still can be had for next to nothing because they signed everything in sight. But even the $20 autos from 1990 are now approaching the $100 range in most instances. As more collectors enter the hobby, there will be fewer and fewer autographs on the secondary market, and eventually I think most have nowhere to go but up in value.
But always refer to rule #1!
