two devices on my itunes account, want different apps for each

I have two devices on my itunes account, an ipad I use for business and an iphone I use mostly for personal. I want to keep only business apps on my ipad and most/all apps on my phone, but every time I try to sync, itunes tries to reinstall all of my apps regardless of device.

Does anyone have a solution for how I can have two devices with different selections of the apps I have paid for without downloading all of the apps to each device? I tried just not syncing the ipad but then it had technical problems and the genius bar needed to delete a bunch of notes from the device, so that is sub-optimal.