As far as I can tell from the photos on
Tim's website, there are four different types of accessories for the floor of the rear:
Cargo Liner ($263 list, $195 from Tim) - Appears to be made of fabric, and covers the entire height of the sides of the hatch as well as the rear of the first-row seats. May be a good choice if you have cargo which might otherwise get the sides dirty, such as dogs riding loose.
Cargo Mat ($109 list, $81 from Tim) - Appears to be similar to a carpeted floor mat. May be a good choice if you want something light weight to protect the carpet back there.
Cargo Tray (Folding) and Cargo Tray (Standard) ($140/$120 list, $104/$89 from Tim) - Both of these items appear to be made of a heavy duty plastic material, so if you haul large heavy items (say, car parts) and you're looking for maximum protection for the carpet back there, these will provide more protection and will be less likely to wear through. It also looks like it may provide some protection against damage from liquid spills; as FTM1 notes above, the smooth plastic surface is much easier to clean than the fabric of the cargo liner or the carpet of the cargo mat. The folding cargo tray can fold so it can be configured for the rear when the third seat is folded down, as well as when the third seat is in use; the standard cargo tray requires that the third seat is folded down. So the choice between the two depends on whether or not you sometimes use the third seat.
So it all depends on how you use the hatch and what kind of protection you're looking for.
In my case, I keep two dog crates assembled behind the second seat (as pictured below). I wanted a cargo tray because I need heavy duty protection, since those crates are metal objects with uneven surfaces (metal bars) on the bottom, and sometimes weigh 60+ pounds each when occupied. Another advantage of my cargo tray is that it has sides about 4" high, so if there is any kind of liquid spill back there, it gets contained and doesn't reach the carpet underneath. Note, I'm not sure whether or not the OEM Acura cargo tray has 4" sides. Mine is an aftermarket (Husky brand) cargo liner, and Weathertech is another brand that makes cargo trays.
HTH