If portability for travel brewing is high on your list, then a manual grinder would be an easy win based on size, weight and also not having to worry about power ratings.
Electric grinders at lower price points are blade grinders which you should keep away, due to a lack of consistency of grind, which will throw off most coffee makers (especially espresso).
Provided you are ok with a little bit of elbow grease, a good manual grinder allows you to experiment and fine tune your coffee pallet while avoiding dishing out more money and counter space.
A good manual grinder will last years if not decades, while an electric grinder will probably not and require higher maintenance as well.
Probably the biggest irreconcilable disadvantage of a manual grinder is the capacity and time to take to produce grind for a family sized brew. If it is more than you and your partner, you may want to consider a quality burr electric grinder in that case.