Yes it's arguable
Technically, the 356 Speedster was introduced in '57. The next Speedster came in 1989. There are more Speedster look 356's out there than original Speedsters. A lot of people mess up on the side marker lights. I don't think the 89's have reached true collectible status yet. So... I want to say that the original 356 Speedster is (here we go again) arguably the most collectible Porsche, but I'm not quite sure it's the most desirable.