I have both so I can give you feedback on both!
I use to have the Uniden in the Jeep before installing the Cobra 75.
1. Uniden 510 has a much louder internal speaker than the Cobra 75.
2. Uniden handset is much lighter and smaller to hold onto.
3. Better visibility of the channel selector to see what channel you are on.
4. Easy to use knobs for channel changing, squelch and volume.
1. CB box that is not easy to conceal....although it's only 2 cap screws to remove it from the mount and take out for security.
2. CB Box in the Jeep takes up about 1.5 inches of driver leg space from the center console if you use the mounting kit from Quadratec
Cobra 75 without external speaker:
1. Concealable mount
2. Fairly quick disconnect to remove the entire CB (since it is all in the handheld)
1. small channel changing buttons right next to PTT button causing accidental channel changing to happen
2. Handset is pretty fat resulting in potential for accidental memory/menu change functions
3. fat handset with spin dials for squelch and volume on the side allow for potential to bump the dials reducing/raising squelch as well as volume levels.
4. CB is only a year old and already the handset cable coating is splitting
5. CB is not easily heard if you are running with windows down at road speed on the hardball and definitely can't hear it if you are top down along with windows. As long as you are off-road you can hear okay since you aren't going an excessive speed with wind noise.
After a year of using the Cobra 75, it has faired well for what I have used it for but glad that I didn't pay full value of it....won it in a raffle. I installed the Uniden 510 into my wife's Armada for us to communicate when convoying and she can hear me much better than I can hear her at times.
Just some input....your choice though!