[pampadori]

I don't have a longhood but i have driven both coupes and my targa back to back.

The targa is much less flimsy feeling when you have that top mounted. Take it off and you will immediately notice the cowl shimmy and move. Does it matter much? not really. it still pulls terrific cornering g's and steers much faster than most other 40 yr old cars.
With the top on, the difference is much less. Louder, yes. but you won't notice it feeling flimsy until you put the car on jack stands and the door gap at the b pillar grows wider. it doesn't do that with a coupe.
Again, a little flex isn't going to make the car must slower in the canyons. not until slicks are mounted and hundredths of a second matter does it become an issue that i'd worry about.

But now i'm reading your signature and I'm curious why you don't already have an informed opinion since you list both a 72 coupe and a 73 targa.