PDforLogic

Still not decided for one platform, with Elektronengehirn I tend to use Ardour on Linux but for Notstandskomitee I still use Logic on Mac. With Jack its easy to route audio from Apple Logic to Pure Data and back. So you can create your own plugins : http://jackosx.com
After you started the Jack server with Jackpilot, you need to select it as audiodevice in Logic to get the routing possibilities. When you activated the autoconnect with physical ports in Jackpilot, a predefined multichannel routing in Logic behaves like before without making changes. Now you can use the in and outputs of Logic to connect to PD, also done in Jackpilot, or use the Jackplugin to insert PD in a channel.
Its also possible to route Midi between applications on OSX. So it has a similar flexibility as Linux which enjoys the blessings of Jack a bit longer.
Pure Data is recommended in the extenden edition which has the Jackpossibilities: http://puredata.info/downloads