AA probably offers the easiest immediate route to status with its Gold/Platinum challenges (see the sticky in the AA forum), but you'll have to requalify the old fashioned way, and they tend to offer the fewest bonus EQM offers. Other airlines like DL and UA tend to offer more bonuses in that direction.

I would pick the airline which you're happiest with overall (happiness in terms of service, schedule, price, etc.). I don't think any airline's elite program at the bottom tier is that much better than another's to justify paying significantly higher prices.