An Astartes chapter just isn't complete without an hulking, fully armor 14, BS 4, assault vehicle that has a ghost. The Grey Knights are no exception here and can take all three variants. They barley make any changes to them either. They all come with the same weapons, transport capabilities and many of the same upgrades. Heck they almost run the same in points cost. The Grey Knight's only pay five more points than there counter-parts. At that price these are quite a steal.
Now they also come with the Aegis, Pyschic pilot, and Fortitude, just like all the Grey Knight vehicles. This only increases the cost 5 points over standard. See, I told you it was a steal.
The only real difference is the upgrades, well some of the upgrades. The Grey Knights get the standard Land Raider upgrades, searchlight (+1), multi-melta (+10), hunter-killer missile, storm bolter (+10) and extra armor (+15). Then they can grab psybolt ammo (+5), psy flame ammo (Redeemer only +15), warp stabilization field (+5), and truesilver armor (+10).
Personally, I love the Crusader pattern. I used to have one and it was a great transport for my Terminators (way way back in 3rd when a White Dwarf article was where the Crusader's points and stats were found). The anti-personnel fire power, frag launchers and extra space was what attracted me. It would with the Grey Knights as well.
A Crusader with multi-melta and extra storm bolter would probably find a way into my arsenal. The problem I would have would be to buy psy bolt ammo or not. The amount of shots this can throw out on the move is great. All those defensive weapons firing on the move is great. Then turn those all into S5 shots. Sure you lose a fair amount of shooting on the move, but you gain so much more damage potential. I would probably fold and grab psy bolt ammo. The amount of S5 twin-linked boltgun shots could do a descent job with transport suppression (Rhinos being the gold standard here). Yes, there is also the twin-linked assault cannon that would also benefit from the psy bolt ammo as well. That might help open some transports as well. So definitely pencil me in for psy bolt ammo on my Land Raider.
There really isn't much else to say here. I mean we all know what Land Raiders are and what their deal is.