I looked into this very same topic 15 months ago. My advice to you would be drive both and preferably drive a 2.5L and 3.0L as well, then decide. For what it is worth I stopped looking at 2.0L after a week then spent 8 months trying to find the right 3.0L. The only advantage I could find for the 2.0L was fuel consumption, but offset against that is the reputation of the 2.0L engine is not good. The straight 6 engine on the other hand is an outstandingly good engine (I believe the 3.0L was voted by industry experts as being one of the best engines in the world). Aside from that, the 2.0L just doesn't sound as good (the straight sixes have a much nicer rasp) and doesn't have the right image/credibility (not that that should matter much). I would choose a 2.2L over a 2.0L every time. I went for the 3.0L in the end not because of performance, but they are more likely to come fully loaded, people who could afford 3.0L new were generally rich enough to buy all the options, people who opted for the 2.0L were likely to have been more budget constrained and could not afford the options, there is also a possibility they may have cut costs on servicing for the same reason and servicing is very important, particularly oil changes.
Good luck in your hunting and I hope you are happy with your decision.
