Hi Luc
In my experience, wands, even more so than machines, are a very personal thing. What suits one person will be the sperm of the devil to another. Others will offer their opinion of what will work for them, but it could well be awful for you and/or your technicians.
If you can, see if any of your local colleagues would be prepared to loan you a tool or two, even ones you haven't considered. It has been mentioned on these forums in the past that a distributor in the Nottingham area will loan you a Wonder Wand for a trial period if you are interested in buying. Perhaps other distributors will do the same?
When I was down at HydraMaster in the summer, I had a play with their standard 2 jet 1'5" swan neck wand (AW29). It looked similar to one that I have, but was vastly superior in every respect. I then tried their low profile, 4 jet 2" swan neck. I was VERY impressed, especially with a Greenie on board. Marginally superior to my own similar spec. wand.
Don't buy any wand on the advice of others. Try them first(not 5 minutes "play") if you can.
Safe and happy cleaning

Ken