It's also more than Decibels of signal as well. It has to do with sensitivity, frequency stability, RF Interference rejection, signal to noise ratio, noise floor, threshold capture, adjacent channel rejection, etc. The list goes on and on. I have plenty of radios, base stations, walkies, ham, Citizen's band, Business band, and as well as entertainment radios, and I can tell you that some of my best sounding radios don't need much signal at all to sound crisp, clear and quiet. On the other hand, those which "peg the meter" are full of noise and bleed-over. Take a dirty signal and amplify it to the input stages of the receiver and you'll peg the meter but the sound will be horrible. In the digital communication world, noise translates to errors, and errors translates to lost data packets, and lost data packets results in fragmentation, distorted audio and dead silence.
It's VERY difficult to "hear" the difference in radio quality between one phone and another now that we're all digital, but when it was analog it was EASY. Sure, there's "call quality" which is a measure of the quality of the sound coming across, but I'm speaking specifically of communication quality as it relates to getting a specific sound or data packet from location A to location B via airwaves with as little loss or distortion as possible. Some radios had fading and hiss and scratchiness in the background, sometimes the noise was so loud it overtook the audio, until eventually the call would drop. And then there were other radios which would hold the signal, cut through the noise and keep the call.
Back in the Analog radio day, when the Motorola car phones were INSTALLED ONLY, and then someone got the bright idea to put a INSTALLATION KIT into a shoulder bag, build a platform of plastic or metal inside the bag to hold the cradle for the handset, and then a hole drilled through for a hole-mounted antenna with a hinge, and place a 12 volt lead-acid battery in the base under the transciever, the "transportable phone" was born. I was in that business from the start. I worked for Bell Atlantic Mobile and was there from the beginning. I had one of the first installed car phones in my car in my entire region. I can tell you lots of what makes one transciever better than another.
I also held the first Motorola 8000X phone that was ever delivered to any Bell Atlantic Mobile dealership in the Philadelphia region of Pennsylvania (the world's first portable cellular phone - invented by Dr. Martin Cooper at Motorola, no surprise there!). I made calls on it. I've used, installed, serviced, played with, owned and assisted others with literally hundreds of different phone models from different manufacturers, and from car installs to transportables to portables to hand-helds, to today's ultra-slim smartphones (my RAZR MAXX to be included). I have experienced the good, the bad, the ugly and the really good and really ugly. I can tell you that no other manufacturer was more consistent with ANY transciever I've ever compared it to than Motorola radios, and I've tested some really high-end Kenwood, Yaesu, ICOM, Unicom, Lafayette, and the list goes on and on. One thing's for certain...more often than any other manufacturer, the Motorolas did what they were made to do...talk and listen.
Sure, as was said above, all companies can put out a good radio at one time or another, and just like all of them, Motorola had their infrequent bomb as well, but nobody was as consistent across the board as they were, and I believe they still hold that distinction.
Edit: shouldn't it also be telling that radio
software tweaks have fixed most (not all) of the problems on the devices that have struggled? The coding and algorithms that go into these things (4G, 3G, 1X, etc.) has to be more complex than ever before. And then there's also Verizon...
And to further piggyback onto jntdroid's comment above, the truth is much of what makes a cellular phone a good phone or data transciever is now on the digital side of the equation. In other words, the radios only take what is coming across the airwaves and produce a waveform of that data into electrical impulses, and vice versa. It's most often the quality of the encoding and decoding of that signal that determines whether the communications are consistent or not. And a big part of that equation is also on the tower side and how it is able to pick up and hold that connection to the portable or mobile phone while it moves hither and fro, and with handshaking and hand-offs transfer to another adjoining tower that has a lot to do with the consistency as well. Some equipment is just better at that volatile connection than others. I like to call it controlled chaos.
You couldn't ask for a worse combination of circumstances under which to maintain consistent communications of high-speed data and voice than cellular communication. You are dealing with mere milliwatts of power (about 250mw on average) from the hand-held or less, an antenna that's surrounded by metal, circuit boards, ICs, a battery and your hands, body, car, house, sky-scraper, earth, and all the while moving, and yet it is able to maintain a near 100% full-duplex communication with only millisecond differences between send and receive, and without losing a beat. It's really quite amazing if you dig deeply and understand what's going on.
So now, you can have the absolute best "radios" on the planet in that phone, but if the digital part of the equation is failing it can "appear" to be a poor radio that's causing the failure, and likewise in reverse but to a lesser extent. So before you start pointing at one or another's "radio" as the culpret in the failures, consider it's now a very small part of the equation, but still mission-critical.