Yes they are stiffer. There are a lot of different one so not all Commander springs are the same. Get Hemi tow package Commander springs. I have them front and rear and can definitely notice a difference. You can usually get a fairly low mileage set for a decent price from a Commander guy that upgraded to an OME lift.
2007 Grand Cherokee Limited | QDII | 3.0L Diesel | S4xC Shackles Mounts | Goodyear Duratracs
Bilstein HD Front/Rear | Rusty's 1/2" Strut Spacer | Hemi XK Front/Rear Coils | HID Projectors