Get a Twin Otter... It's just a big BN2 with 2x PT6's, best of both!
Seriously though, I'd go for the Bongo because it logs time in the magic column.
Turbine time is probably 'easier' to get than the 500 multi because the majors will take people with no turbine time.
And if you are really after turbine time just to have it, go for the Van after you have a decent chunk of multi.
If you are looking at the Van to operate RPT and overwater etc, heaps and heaps of crap to wade thru by way of ASETPA or something like that.
Heaps of Bongo time... Rugged, reliable, dependable, relatively simple machines. Feels like a man's aircraft, it aint a princess like the 208.
Little bit deaf. Somewhat desensitised to "odd noises" and "strange vibrations"
But heaps of fun
Just remember, 65kts!