Chieftain is arguably even better than the challenger for pve because of the overall larger hardpoints, and better agility. It doesn't have the same overall DPS as the challenger (well, that's subjective, due to its speed, it's arguable that it does, as it gets on target faster, I digress), but two large hardpoints is not be overlooked, they get a good piercing bonus and therefore are worth more damage against the ships with the higher hardness ratings. There are loadouts that suit each ship well because of these hardpoint layouts. For example, three rails on the bottom of the challenger is beautiful, but it's difficult to get a good PA configuiration with 3 mediums underneath and a large on the top. The Chieftain with its two large hardopints right on top of one another is a SICK PA platform, especially if you are good enough to also land the belly medium, too, it's a powerful burst volley. The armor is comparable to the challenger minus about 15%, which is still massive overkill for pve. It can be built to exactly the same principles as the build I posted earlier, it has quite a bit more speed and pitch (which actually sometimes doesn't help, depends which weapons you're using, I find it easier to fire rails from the challenger and the Krait than I do from the chieftain, its pitch and yaw are so aggressive) so you can get on target faster. It also makes an exceptional Pacifier platform in pve (it's a bit drifty for pacifiers in pvp unless you are an EXCEPTIONAL pilot and shot) for the same reasons. Which brings me to the final point. The Challenger has weirdly good space grip. The Chieftain is very drifty. Sometimes, in FA off if you get it right, you can pull some extraordinary, almost FDL-esque maneuvers in the Challenger, just without the outright speed. The Chieftain on the other hand, flown FA off, becomes quite predictable and doesn't change direction very aggressively (again, with teh exception of great pilots, the Chieftain is a very agile ship and can really dance, but again it's difficult to get the best out of it in this regard compared to say, the FDL, or even the challenger, due to that low 'grip' factor)
The Crusader I'm sorry to say, is just rubbish. Enough said about that. I can only assume that in giving it a fighter they felt that was justification to completely gimp the ship in other areas (bad module sizing, horrible hardpoints, slow, ew, just ew...). Good pitch is about the only positive thing you can say about it.
It;s so horrible on paper I haven't even tried to build one, so if someone disagrees, please, try to change my mind.