I assume you are not referring to a 22-45 with PACLITE.
I have also considered a PACLITE upper and have handled several MK II's with the 6" barrel. Compared to the MK II Competition model, the balance is shifted slightly to the rear, different, but owing to the angle of the Ruger grip, very comfortable and natural. If you want to do speed shooting, a PACLITE would shift the weight center more toward your grip and reduce polar moment.
My recommendations: For routine target shooting - a MK II Competition or Govt Model.
For speed shooting, or for a lighter weight pistol to pack in the field, purchase a MK II with standard tapered barrel and add a PACLITE.
I would not convert a MK I and with all the good used MK IIs around, never purchase a MK III.
Let us know what you decide.