I would recommend Physical Shiftry, since it's attack is higher and learns some good physical dark moves like Foul Play and Knock Off(you get knock off in ORAS, btw). Plus it has Chlorophyll, which is a really useful ability in sun teams. In the sun with chlorophyll, you can have a really fast Pokemon. Also, for suicide, you can pack in explosion(learnt as a seedot) for big damage. And last but not least, you can have Seed Bomb in which is the best physical grass move it can have. The choice is yours. I'd recommend Physical Shiftry though :P
Hopefully this answers your question.
Hope I helped!(ish)