Even when you record at 24 bits, the files will be changed to 16 bit for CD's.
Most people convert to MP3 which is even further down the resolution scale.
If most people can not tell the difference between a 16/44.1 wave and a 320kbs MP3, you will not hear the difference between the 24 and 16 bit wave.
I am not trying to be flippant or minimize your question. That may or may not answer your question but for most people this is not something that matters much to the listener. I certainly don't worry about it.
I think MC6 treats the final export a bit differently than some of the other Sonar offerings and even earlier MC programs. I believe 6 has a certain limited number of exporting presets. Some of the others do allow settings of 24/44.1 to export but I'm not 100% sure it stays at 24 bits. I would have to look into that deeper.
I pretty much let it default to 16/44.1 since I will be converting to MP3 at some point anyway, and 16/44.1 is, as I mentioned earlier, the universal default to CD quality.
BTW: I send stuff as wave to producers too. I've had a few things signed. The most important thing to them is the song and does it work for their use. As long as the recording is well done and fits the scene.... the quality can be rough or polished. and unless they are specifically asking for some sort of "different" format, the 16/44.1 will be what they are expecting. Several of the things I have had signed were in fact "lo-fi" recordings (intentionally).