I think yes, it matters. If the device has unncessary bezel space, it is going to be that more difficult to use it. Even for simple things like answering a call with one hand. The difference between having .5" to for a call button, and 1" is huge.
Fair enough. If that is the case, then I would think that you would want it to be less wide. Wider devices are more difficult to fit into pocket/purse than taller devices, I would think. I do think it's comical to use the "one hand" convenience reason for a phablet because there is no way you'd be able to use it with one hand in most cases, whether the bezel is .5" or .6". (I don't think the bezel size diff between different phone models is as drastic as .5" to 1.0")
Again, for a phone, I would think that a wider device is more detrimental to the portability/usability than the vertical height. No matter, I guess if one feels that 5.5" iPhone 6 being taller is not good and dismiss the fact that the Note 3 is a little wider, then people will go for the Note 3 instead. I highly doubt this. If you are already an iOS fan, this won't make someone choose the Note 3. If you are an Android fan, you will pick apart the fact that the 5.5" iPhone 6 is taller and somehow find reasons to criticize that it's not wide enough. Apple has chosen this screen aspect ratio and they are sticking with it for ease of app development. If this aspect ratio and its resulting phone size dimensions bother you, then don't buy it. End of story.
Personally, I don't care to use phablets. I am intrigue by the 4.7" iPhone 6.