The size of the battery pack you should purchase depends on how far you intend on travelling. We have found that many first-time e-bike buyers purchase the smallest battery option, but then use the bike more than they initially planned. E-bikes are fun to ride, and users enjoy spending time on them.
Repeat buyers typically buy the largest battery within their budget, and this is a common recommendation for any electric vehicle. It is better to not spend your time worrying about whether or not you will reach your destination.
Larger battery packs also tend to last longer as you are less likely to discharge the battery below 20%.