I would try the mechanicals first. I have not built or flown a VQ model yet but I would agree with Tomas, I don't think he would offer his mechanicals if they we poor units. I fly and have flown a lot of the Kyosho warbirds with the stock mechanical units they come with and have had few if any problems. Mechanicals are not really hard to set up and I can help anyone who needs it. In most cases, mechanicals don't work right because people don't have the proper amount of throw and the retract is not cycling lock to lock. In a 40 size plane you can use a $30 Hitec servo with no issues. I too, like most, prefer the JR servo, but have come to realize I don't have to spend that much money to get the job done.
The cost of mechanicals is less than half of air units. On larger planes I don't think there are many good mechanicals available so air would be the way to go. The Lados, when they become easier to obtain, will be better than air units. I have air units on my Byron P51 and it is a pain either to manually pump them up or haul around the air compressor. If you try the mechanicals and then find you don't like them, let me know, I'll buy your "used" retract servo!