No matter what you do using two daws together will always be finicky,the main reason to do this is when you want or need certain features durning any production from one or the other,for me fl studio is my main focus for its flexibility with midi programming,all matters pertaining to audio,editing,recording,etc etc.. Are focused in sonar,basically all audio is bumped into sonar,all the final arrangement,mix and mastering take place in sonar.in fl studio things get so crazy and disorganized it's nearly impossible to get it sorted out....we'll if you produce like I do that is,and this is a problem for a final mix but that's were sonar is my savior from myself lol.also multiple takes and compin in sonar totally invaluable for recording.
Sry that was more a rant than anything,long story short working with any two daws together on a track from new project to finished track there will be problems.
things like rewire and vst versions are awesome but don't forget that these are different competing company's,they only support the standards everyone elts is they do not support eachother.Rewire and vst versions are tools to make interchanging project parts between softwear and to use effects and or synths that are native to said daw only possible.