The MB E400 Cabrio is more modern and luxurious than the BMWs, but the MB is only available with a V6 twin turbo that makes 329 hp, not much by today's turbo standards. Car and Driver says that at low speeds, the 9 speed transmission is jerky. The engine is just adequate, but they wanted a little more power and maybe an AMG version. I'm guessing it would ride a lot smoother than the BMWs. The interior is definitely better in the MB.
The BMW is much more a driver's car than the MB. Expect a firmer ride, but nothing harsh. More tossable. Has an older interior and less tech.
The Audi A5 Convertible is another choice. It is the lightest one on the list at 4000 lbs. I like the conservative styling more than the BMW, but the MB is the classiest. Good balance of handling and ride.
Hardtops are not as common as they used to be and most are out of your budget. The Infiniti Q60 had one. The Miata RF has one and is a great car, but is not that fast and does not say you have money like you probably want. The 4 series has one and is a good choice.
The MB SL 450 and SLC have hardtops, but both have dated interiors.
If you are older and are looking for a comfortable convertible cruiser, the MB E450 Cabrio is the best choice in your budget.
Why do you want a hardtop?