Stereo or dual mono volume control?

I would go with stereo regardless of whether your ears are different. If one ear hears better than the other then I would just change the gain on that amp channel so that they match up. It would be much easier to do this once than have to constantly be fiddling with two knobs to try to get it just right.

One thing to keep in mind - if your brain is used to one ear hearing things at different levels, then forcing them to balance may sound unnatural to you. Better to have the two channels with the same output levels, imo, unless you are overcoming specific damage or a medical imbalance of some kind - not a natural difference in perception. 

I am not a fan of altering the volume till it is perceived as the same but in my opinion it is better make both  L and R  as mono. It may be more a challenge to tune it to your ears but the sq loss from the additional components would be the same for both ears making it negligible.

EDIT: a better idea is to use a master volume and control for each side.

I think it's just a hassle compared to say a balance control as once you have it where you want it, going up or down again without losing the settings would be a bit of a pain.

I have seen an unusual mechanical solution to this, where each volume knob had a cog, and there was a gear on a shaft that would flick up or down and engage/disengage. So you adjust each channel seperately and then engage the cogs together so they both move equally.

I think if a volume control IC with rotary encoder/s was used it would be ideal, but hard to implement and code and displays for them is much more case work.

That would allow for the ultimate flexibility as you would remove that problem and allow for virtually any style of control you want, could have two that could be tied to each other by pushing the encoder in or so on, could even say preset what sort of bias to the balance you want in the code or have it as a configurable parameter in a menu etc.