For instance, can you tell what would be the expected operating difference between these two Cams in terms of power band, torque or whatever?

ECH 109 2303
HYD. CAMS
5 CYL. 4V HYD. CAMS WITH
GEAR.LIFT 11.20/11.20,
DUR 266/266,LOBE 112/112
DUR 266/266,LOBE 112/112

ECH 109 2304
HYD. CAMS
5 CYL. 4V HYD CAM W/GEAR
DURATION 272/264.LOBE CE
112.LIFT 12.00/11.00
112.LIFT 12.00/11.00

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Shift the power upward, the top end pull will be CRAZY if you can get the timing and fuel maps setup. Will be able to pull beyond 7500rpm. Both would require cam followers other than the factory 309AD items, as they will just compact under the quite large lift and high revs.

I'd go with a 264-272 cam with around a 10mm lift, should be able to use the stock followers at that point. I can try to find out if the guy up in Findlay can get a hold of his cam/head guy, to stick one of the 7A heads on his bench and figure out how to get them to make the power where it should be (3k-7.5k) and possibly still get you to 200hp or more (Mark W.'s got one of the only AudiSport/Kolb built 2.48L 20v's, and is "over 300hp" at the crank with it on the requisite 104oct).

Longer duration, with more lift will produce better top end power. Your tradeoff will be low end torque to an extent. All factors of any cam profile depend on what you want to do with the car and what modifications you already have. Goodluck with your decision!