I've never owned either car but i've driven the C43 quite a few times and it is a special car.
No offence intended to any owner, but i seriously think the C43 is a bit of a marketing ploy. Yes its said have more bhp, be quicker, and have better equipment (which i'm not doubting) but i really dont think even with all that in mind, its THAT different from the clk430, so dont count it out.
In terms of quality, they both should be identical, as Will was saying earlier, they shared the same compnents, and they even share the same chassis. Maybe the C43 will have a better spec (seats etc) and better equipment (shocks, alloys brakes etc)because its an AMG but you have to budget for replacing them as they cost a bomb, whereas the Clk430 may not cost as much (correct me if i'm wrong here).
The CLK is a good-looking old-school coupe, the 202 is a good-looking old-school saloon. Your not losing either way, so its your choice.
Note: I used to fuss over book times to 60, but when your rolling around in a 4.3 V8 with 300-odd bhp, who gives a toss how long it takes you to get 60? In my car, i pull off the line at my own pace... and if someone next to me wants to give it a go while i'm already rolling goodluck to them...