A quick lesson on shock absorbers... no quad manufacturer makes shocks.
They purchase shocks and then build the suspension around them. There are a handful of shock manufacturers. The most common on jap quads is showa. Showa manufacturers extremely high end race bike suspension (honda's GP team sometimes uses showa equipment) to the cheapest piles of doo possible. Anywhere in that range you can find good examples and bad examples.
The suspension systems you mentioned are virtually identical. The late model LTZ400 suspension is a remote reservoir unit but the older ones are not. The rear shock on the 450R, 400EX, and LTZ400 look identical with the strange placement of the 450R reservoir as being a little off center (still works but you have to trim a mounting tab off the frame). The front shocks are, probably, identical units. Sprung and valved nearly identical probably.
The trick to a good swap of factory shocks onto modified blaster suspension is to find low hour units. Not such a big concern which quad they came off of as it is how bad they were beat on on the other quad before you got your hands on them. If you find a set of low hour take-offs, either of the choices you mentioned should be a huge improvement over the factory suspension