I always have a pocket pad on me, more often than not it is my Midori w/ customized paper. I compulsively try different brands and set ups/ style.
I do in general prefer the refillable ones. There is something about having same pad accompany me all over the world and grow increasingly familiar in touch and sight for me.
There are some great non refillable pads out there too. Within my diverse collection of pocket pads they all fall within the 3×5 size range.
One thing I like about mixing thing up pad wise is that although they all are the same size each company’s paper has different properties. My voice remains present but each type of paper adding something of its own property’s to the mix.
It is akin to a musician using different instruments for different types of songs (think for example, Miles Davis or Jimmy Page)
Here are some quick sketches done on pocket pad of company I just discovered.