The Conquest has a wider cabin and with -10 engines is hard to beat performance wise.
From a maintenance standpoint it has the same system flaws as the rest of the 400 series Cessna. If your boots are inflating in flight, if the cabin goes to max diff on rotation, if the oxygen system is leaking in the headliner? Its all because cessna ran all the heat and a/c ducts without insulation and it has steel spring stiffened spring wrap. All of the vacuum and oxygen plumbing is aluminum tubing and crosses the ducting in many places which causes corrosion and system leaks from duct sweating. Seen a few conquest and 414A's with oxygen leaks from this and inflated boots because the cabin pressure was going into the vac system and one with a pressurization problem. That just off the top of my head.
From an owner operator view the king air wins, tougher aircraft flys smoother and still has strong manufacturer support since they still build them. Cessna 400 series parts start getting scarce, I have 5 414A's on our certificate, a couple 414A customers and a couple king air customers.
A friend of mine has been in both a conquest 2 and ka200 with some special equipment that is more sensitive than the aircraft flight Instruments and says the ka200 with raisbec strakes is a more stable flight platform than the Conquest with aft stakes installed.