If your aw29 wand has the main tube sticking into the head at all, you will have some really f---ed up airflow. Mine has this issue, but running a porty that has 100 cfm at best, it wasn't an issue (there was enough clearance for the airflow). Hook this same "crippled" wand to a TM (mine has a 36 blower), and while you will get more airflow, the tube sticking out into the wand head restricts airflow.
I recently got a 14" bentley wand, and it is a night/day difference. I see almost no difference in the lift at the machine. The needle in the gauge moves about 1/32 of an inch. Hooking the aw29 with a vac attack (2" to 1.5" adaptor), I see almost 1.5" more lift being wasted. Both wands have hole
GreenGlides, and are about the same resistance to move on the carpet without the vacuum hose attached. Hook the hose up, and the aw29 doesn't get much harder to move, but the Bentley grabs the carpet. I can leave the carpet MUCH drier with the Bentley doing NO dry strokes than the aw29 with THREE dry strokes. This was with the aw29 at 250-275 psi, and the Bentley at 500 psi.
Would I use the 14" Bentley or a greenhorn on my porty? NO. I would however use them on a porty if it was an M5 or similar specs, or if I were using a 3 stage mytee vac booster for added CFM.
Short Version: If you have the water flow and vacuum to support a Greenhorn, 14" Bentley, Prohem TI, or similar wand: DO IT! If not, then a Greenhorn Lite, 12" Bentley, or other 2" tubed wand that is 12" wide is still a good idea. If you have a TM, and are running a 1.5" wand, GET A 2" WAND!!! I highly recommend the Greenhorn wand.