May I have a quick rundown how MK IV is better than MK III? Any chance it has a higher range or an additional internal slot so that I can make it an exploration ship with hangar and two tanks?
EDIT: Wow, it actually has quite a few additional slots and at marginally lower jump range you can get a lot of stuff installed. I guess I'll switch.
I see the MK IV as a smaller Python, as it has a enough extra slots to make it a very versatile ship, much like the Python.
It has 4x size 4, 2x size 3 and 2x size 2 slot, so that is 2 extra slots over the Mk 111 - plus it has an additional small hardpoint with much better weapon placement than the MK III.
Mk IV loses out on jump range and speed, but with a bit of engineering, you can close that gap significantly.
Great little ship and I like using it because its a little different and makes a nice break from my large ship fleet.