Monoblock, because its cheaper and its better looking.
It's personal choice, but....
I cringe at 18" on w201. Don't think the body style and chassis size supports this.
Cladding helps, but I just don't see it.
Would like to know your choice of rubber.
And I cringe at slammed.
Love alamandine red.
To know my bias...
I'm back-and-forth on this 17" SLK (17.5 et37) in my inventory or retaining an 16" Evo1 knock-off.
Nice thing about your monoblock option is that it picks up the fake bolt cues as on the SLK wheel and it has some lip (at least in the 9" photo).
I think this is important because the wheel should match the aggresive intention of a cladded w201 (ala 16V).
The 5-spoke is a little too clean and flush.