The DVR-108 from Pioneer is excellent; however, is it not natively supported with OS X. That means you won't be able to burn DVDs straight out of some of Apple's iApps. There is software out there that "patches" your drivers and will allow full burn support for this drive, and that's completely up to the user -- I prefer not to "patch" anything. Support for this drive will probably be included in future updates/releases of OS X.
The DVR-107, which does not do dual-layer discs is completely supported by OS X.
Long story short: if you need iApp compatibility now, go with the 107. If you just need basic DVD burning capabilities, or dual-layer support is important to you, go with the 108.