Best way to share audio files between different DAW platforms?

Easy, just make sure all your audio clips in tracks start at the beginning of your project. If one or more tracks don't, just grab the end of the clip and drag it back to the beginning and then bounce to clips. That will put silent audio back to the beginning of the track. 
 
Also make sure the tracks aren't split up into many clips, select the entire track and bounce to clips to fix it as required. 
 
Also if you have melodyne or drum replacer or any other region effect, you'll need to render those can bounce everything to clips. You're looking to get one clip per track that starts at the beginning of the project. 
 
Then export to wav, keeping whatever bit rate you already have for the project, and export as "tracks." In the export dialog you can choose whether to have FX or not, just check all the boxes you want and do the export. 
 
You'll get a wav file for each track, either in stereo or mono depending on how you select that in the export dialog. I would select "no dithering" since you'll be exporting them at whatever bit depth, but it really doesn't matter. Sonar is smart enough NOT to dither if it's not required even if it's selected.
 
On your other DAW, import a track at a time from the exported files and viola..
 
gabo

No worries, I do a lot of this as I work with a group of people that live all over. We trade songs and do our parts and all use various DAWs.
 
When we first started we were very concerned about it. But with experience, it works beautifully and is really dead easy to do. Just takes a bit of practice to get used to all the export options and thinking about what comes out the other end depending on how they are all set. 
 
gabo