Hands down the Learjet 31A is faster and more efficient for that type of mission.

I have flown them both and have managed and performed maintenance on both (more experience on the Lear). The 400A is ok but dumpy and not as good in X wind.

The Lear can (full of fuel ) with 4 pax climb striaght to FL 450 no problem.

The 400A cannot even come close to that performance.

Any airport with 5000ft will do for the Lear. ( Aspen is another story but do-able).

If you need a pilot, copilot or pilot /mechanic /maintenance manager, or pre-buy inspection.

Let me know ,I can help.