I have the Q2-15 with DLT2000 drives.  Great product.  Nice form factor and 
good ratio of drives to cartridges for many applications.  No ADSM support in 
Windows NT, but have the robot identify itself as a Q7 and it works fine (if 
you ignore the element numbers as described in the ADSM for Windows NT 
documentation.  Correct information: Drive 1 - 116, Drive 2 - 117, Robot - 
121).  Typical mount times are about 90 seconds from the time ADSM starts an 
operation.  The vast majority of that is tape mount time, not robot time.  The 
robot is fast.

Your choices have a wide range of drive to cartridge ratios.  I would think 
this ratio would be more important than the robot type in the final selection.  
I've used the Q7 and the Q47.  These are both great products as well, so you 
might add these to your list.

Kelly