Grow what you will use!
Depends on what you will be using them for, will you be making sauces, canning, smoking, dehydrating, stuffing, appetizers.
For me
I would pick one of the other for Marconi or Corno Di Toro, unless your getting the Corno Di Toro Giallo for color
The Marconi are very Similar to the Corno di Toro Russo (red) but in my opinion the Red Marconi are better. The "Giallo" has been a heavy producer for me.
Giallo (Yellow)
Red Marconi
There's also a Giant Marconi but to be honest I think it's the same as the regular Red Marconi and may be a seed mix up?.
Jimmy Nardello makes for a fine sweet frying pepper.