they both seem to be the same to me, as they have the same weaknesses, but it really depends on what you need, physical attacker go with khan, sp.att go with porygon.
heres a something i would probably do with khan,
early bird, jolly @ muscle belt(or whatever item increases att. power)
fakeout
rest
dizzy punch/headbutt/strength/crush claw/rock climb
crunch/shadowclaw/drain punch/brickbreak/hammer arm
3rd slot is your stab move, from accuracy to power
4th sloth is coverage, pick witch ever seems more important depending on your team
and something along these lines for evs
240 evs in hp, or 236, which ever makes the hp an odd number
200 att evs
60 speed evs
4 def
4 sp.def
if you going to go with hammer arm or if you want to try out a different ev spread, switch to adamant and leftovers and drop all speed evs into def and sp. def
i havent tried this out myself, but see how it goes and tell me if its any good