That's the two grills I have. They both get hot as hell with lump charcoal. My guess is the Weber can probably get a little hotter based on being deeper and you can load more charcoal. However when it gets that hot, with a big load of lump, it's actually kind of scary, because the metal is so thin. You can also burn the paint off if you don't have the charcoal in a separate box with some airflow between. I have the Slow and Sear, and that's kept me from damaging the paint when its gotten away from me a few times.
The PK is a thick non-painted aluminum, with nothing that could get heat damaged. It's pretty shallow compared to most grills as far the load of charcoal, I'm not positive whether you could load enough charcoal to get it to like 1000 degrees, but maybe. I don't think you could get there with just half a grill of charcoal, if you're doing reverse sear. However, you can get it plenty hot enough, and if you load it with charcoal, the grate is basically sitting right on the coals, so it's going to be as hot as you need. It's very good for reverse sear, because even though it's small, the cool side stays pretty cool so there's a real demarcation between warm and blazing hot, so you can really manage it. I just don't use it as much as the weber because of the small surface size...I keep telling myself I will use it more when I'm just cooking for me and the wife.
I have grill grates, and I used to use the hell out of them, but I hardly use them anymore. They're a pain to keep kind of clean, and I've decided my preference is to just put the steaks on the hot side really, really hot (700+?) and get an all over sear. There's no doubt they make fantastic grill marks, but I try to char the entire side. It might be my imagination, but I feels like you lose something with the grill grates separating you from the actual flame and searing just on hot metal.
I'd highly recommend grill grates for anything that doesn't get super hot like a gas grill or a pellet smoker, but if you can really get the temperature up the results with the grill grates are prettier than they are tastier.