That really depends upon what you're trying to do, and where you're trying to do it. A King Air 200 is very hard to beat for an air ambulance platform. If you're going a long distance then a Lear is fine, but also considerably more expensive to operate and maintain, and is further unable to operate many of the places that the King Air can fly.
I've operated turbojet (including LR35), turboprop, and piston equipment on ambulance operations, including some very rural operations, and of all the aircraft I've used, the BE-200 is probably the best all-around suited to general ambulance work.
If it's a long flight or a time-critical flight such as organ harvest work, then a lear works well, though a Lear isn't the most comfortable for long distance travel, either. If you're using short or rough fields, though, the Lear isn't your best option.