I think it's better to save them as jpg (quality 80% should be good enuff) since you are store more in the CD-R. I doubt the difference when you print them out will be perceivable, unless you are blowing the pic up really big.
There are differences although the difference is minimal. It really depends a lot on whether you have adequate resolution to print, if you are near the 300dpi recommended printing resolution then high quality JPGS should be very very close to TIFFs for all intents and purposes. But if you are stretching the resolution front then JPG compression artefacts get "enlarged" and become more obvious. Although I personally shoot nothing but JPGs anyway, so I personally don't think it's an issue.
Once, my regular lab showed me 2 10x15" prints, one printed from a TIFF file, another from JPG. Even under close inspection (though I did not use a loupe -- no one looks at prints with a loupe anyway), I can't tell the difference. As long as your source file is of sufficient quality, it should be okay. A well captured JPEG still beats badly captured TIFF. Don't be too hung up over the RAW vs TIFF vs JPEG issues.
I had some .TIF files saved with LZW lossless compression on and the first lab couldn't get it printed right and the second lab I asked said their machine can't open the file. They advised me to save it without any compression.
Otherwise my previous experience with a "normal" TIF file printed alright.
If you are editing images save in a lossless format. Instead of doing multiple saves in JPEG, save in TIF. The final files for the lab can be saved in JPEG if desired (and I think preferred by most labs).
I'd suppose the general rule is to save at the best quality settings if you can, though High setting is good enough too for your personal experience with 4R prints. If you have to burn another disc in order to give the lab all the files, that's a tiny cost anyway. There's also CDRWs which might be preferable.