I am wondering what is a good way to train against computer opponents? Right now I use the stockfish engine on my iPhone 5. I get out a real board and make the moves on there. I am about 1400 so I set the engine to 1500 to play against. It beats me most of the time, sometimes I can draw and one time I won. Is this a good way? Or would I improve quicker if I cranked it up to 2500 and let it kick my butt.

Better start at same level with you. Say set it at 1400.

Depending on how you understand the complications and how much volume of analysis you can handle, setting it at a higher level is also good.