wekick is pretty proficient in the griddle department but the griddles are technically very different.

Thermador uses a titanium coated griddle heated by an electric element. There are a few pluses to this arrangement. First it should be very even because of the electric element and have more precise temperature controls. Because the griddle itself is non stick coated it'll be easier to maintain as well. The negatives are that electric will be significantly slower to preheat or change temperatures since its a lower powered griddle. Recovery times (time to get back to temperature after placing food on griddle) should be ok since the griddle is a thin pretty conductive material.

Monogram uses a Rolled Stainless Steel plate (I cant remember the thickness) with a gas fired infrared burner. The plus here is going to be heat up time and good recovery times (partially because of the plate thickness, and partially the gas burner). The drawback will primarily be cleaning since its not a coated griddle. The other plus to the monogram griddle is that you can level it independently of the range. So if you need to pitch it back to front to help cleanup or grease roll off, you can do that. Im not aware of any others that offer this.

If you ask me though, I always recommend to get an all burner range and invest in a good quality removable griddle plate. The results will be close enough, the cleanup will be much easier, and when you aren't using it (which will be more than you likely will use it) you will still have those extra burners.

I debated between the 36" Thermador with griddle, but ended up going with the six-burner (dual-fuel) so I could use a griddle over the gas burners. The star burners do an excellent job of heating my panini pan (top and bottom). I put each piece on a burner to heat them up and pressing a panini sandwich takes about two minutes.