Was originally leaning toward the bigger option, then switched over to the smaller one. My advice honestly, just make sure to grab at least one, because doing this properly involves testing costs that add up fast, easily equivalent to several kits worth of budget on testing alone.
If the weekly amount is likely to stay above a couple milligrams, bigger vials make more sense. Below that, smaller ones seem better. That's basically the logic used here, since deciding felt genuinely tough. Just try projecting the likely dose trajectory over the coming years, then based on personal risk comfort, set a mental shelf life for each vial somewhere between two and four months. Four months is the usual standard, but a more conservative two months gets used for planning purposes instead. Better to have it sitting unused than to be caught short later.
Hope that tracks.