IMHO,
C208, expensive to buy, very very reliable, a little underpowered in high ambient temperatures, parts support in fantastic and a real pilots aeroplane ( comfortable with aircon that works a treat ) and most importantly passengers love them.
PA31, cheap to buy, very very expensive to maintain and very unreliable. part are reasonably easy to source, uncomfortable piper piece of crap to fly, aircon do not quite cut it, on one engine, poor performer, in my opinion a C402C is a better product.
Cresco ( have not flown the XL ) , heaps of power, cheap to buy, very reliable in the hands of good engineers, parts support is attrocious (PAC), perform much better than a C208 and there are some interesting options available, aircon is good, dual tyre MLG, king avionic including autpilot etc etc. If you could get a contract with the manufacturer, that commits them to provide a proper parts service, they will prove to be far better than the C208, and you can use full reverse in flight
.
Just be aware if you are looking at this aircraft for mining contracts, talk to the auditing company regarding their needs, some insist on multi engine.
If money is not an issue, buy a B200, with the analog instrument panel.