If you’re a musician with a small pedal setup and you plan on keeping it that way, then a miniature size board will do just fine. They’re light and do the exact job you expect of them. This kind of pedalboard is ideal for busking, where you don't want to haul around something too big or simpler Swiss army knife setups. If you could see yourself expanding on your array of effects, it’s worth investing in something slightly larger – even if it means you don’t fill the full board space for the time being.
Regular gigging musicians will benefit from a medium-size board. They’re not excessively heavy and you can pack in plenty of effects. Those of you who like to use expression and wah pedals will need a mid-sized board just to fit it one on comfortably. PSU mounting to power several pedals is also an important factor you simply couldn’t address with a smaller pedalboard.
And finally, those players who want everything at their feet. You’ll need either a premium board such as a Friedman Tour Pro or a larger option from Pedaltrain or Rockboard. Modern digital pedals can be quite bulky and take up the space of two or three standard stompboxes. Preamp pedals are also hefty things and you’ll need the space to accommodate.