For the flexibility I would go with 2.5ohm. You could get the 3.5, but then you'd be limited to HV only. I wouldn't go much lower than 2.5 though.
Personally if you're going with a red drip shield, I would get a red IPro with chrome caps, then top it off with a chrome drip tip (510 atty) or if you're willing to change the drip shield, go with chrome drip shield and red drip tip. *shrug* all personal preference though.