I've been scanning for almost 35 years. I've said it before, and I will say it again: It is very difficult, if not impossible, for find one single antenna that performs equally well on all bands.
You will almost always get better reception on an antenna mounted high up on an outside mast, fed with good quality coax cable, than you will using any antenna attached directly to the scanner. However, if you want or need to use a rubber duck antenna attached directly to the scanner, the Diamond RH77CA is a good choice, especially for the VHF high and UHF bands. On the 800MHz band, it isn't much better than the stock antenna. For 800MHz reception, the Radio Shack 800MHz antenna does a very good job on 800MHz, but just so-so on the UHF band, and no better than the stock antenna on VHF high. So you are back to the compromise again.
The best all around rubber duck antenna I have used is the Austin Condor. Its main drawback is that it's fat and ugly, but it does work pretty well. No, it does not perform better than the RH77CA on VHF and UHF, but it does do better on the 800MHz band, which is the main reason it is better overall.
So what do I use? All of the above, and then some! I have a wide variety of antennas, accumulated over the years. My "main" antennas are the Austin Condor, the Diamond RH77CA, and the Radio Shack 800MHz antenna. These will work well for most people. If you only want to listen to one single band, get an antenna tuned for that band. It will work well for the band that it's tuned for, but will be a compromise on most, if not all, other bands.
As always, these are my experiences, your results may vary.