The ONLY relevant questions anymore are, "Can this computer handle:
- HD video editing
- 3d rendering
- Mass ultra hires photo processing
- Games set to maximum settings"
The OP may take you seriously, so you should avoid this kind of exaggeration, especially regarding any computer made in the last decade. If the OP is getting a mac, they may want the ability to use current software which means PowerPC (which was made within the last decade) is a very poor option.
Gaming doesn't run well on a macbook air no matter what. I've seen it, and any game from the past couple years can bog it down at times on normal settings. 3d rendering isn't ideal on a macbook air or pro. The gpus slow down considerably at higher poly counts, although I think it's more of a driver thing (OSX graphics drivers were never designed for 3d work).
My suggestion would be start with a 13" macbook air or pro. If you're having to do homework on it, you will appreciate the extra screen real estate if you're working on something for an extended period of time. I might suggest getting one of these, then getting the ipad later if you feel you need it. I don't see how anyone could perceive themselves as anchored with a macbook air. The ipad seems like an advantage primarily in situations where you cannot place a computer on a stable surface. The weight difference isn't that bad, and neither will fit in your pocket. Going with at least a 256GB drive option is definitely a good idea.