...Which would you recommend? I use mostly cc3d for flying without gps. ... now using the Revo ... My next project is setting up OSD. Do i set it up with the FC or can i just set it up on the fpv unit. Because i have my fpv unit (cam/trans) all in a easiesly moved from one unit to another type set up.
The cc3d has no use for gps except for telemetry or an osd. And the "op gps" units don't work with cc3d boards, only revos.
An osd really needs to be connected to the FC so it can display aircraft attitude. The wiki article
https://librepilot.atlassian.net/wiki/display/LPDOC/MinOPOSD+setup tells about the only osd that I know of that works with LP. The smaller one shown has the same features as the larger one, it's just a newer, improved board layout. The first connector configuration using 4 pin connectors would work for both the cc3d and revo. You could mount the osd to your movable fpv package and just unplug the one connector that goes to the FC. You wouldn't have gps position on the osd when used with the cc3d unless you buy another gps that works with the cc3d but the rest would work.
The gps that I currently recommend will never work with the cc3d and only works now on the revo with the next branch of the software or the next release when it comes out. It's the DJI Naza gps and it's clones. It has an onboard mag sensor that sends data to the FC on the same cable as the GPS so it doesn't take up another port like some other GPS with external mags do. Again, it doesn't work now except if you compile the next branch yourself but will work on the revo only in the next release.
...i don't have a op link modem. Would that help or is it more for the wireless link to control from the computer?
The oplink can be used to control the copter but it's primary purpose is to send telemetry back to the GCS on your laptop. It's also handy because you can change FC settings through it without hooking a USB cable to the FC.