Chargers can vary greatly in the average time it takes to charge your vehicle although the most common chargers anywhere from 2 to 10 hours to charge. The faster the charge capability usually the more expensive the charger.
Portability: This depends on the use. If you’re going to leave it in your garage and not take it in the car, then portability is not as much of a factor. The less portable models can be less expensive but, may have more features and will probably be larger and weigh more. If you plan to take the charger with you which is common, particularly if the charger has a jump start feature, then size and weight become a consideration unless you have a large SUV or something like it with plenty of storage room.
Not all battery chargers can charge all battery types. Common battery types include lead acid, flooded or sealed maintenance free (very common now), in either AGM (Asbsorbed Glass Mat separators) or Gel cel batteries. Pay attention to what type of battery or batteries you will be charging and select the appropriate unit.
Most battery chargers come with this specification. Peak amperes is the measurement of the highest peak of current draw over one millisecond or over one one thousandth of a second. The higher the peak amperes, the more current can be drawn by the car battery charger without damaging it. So it is usually a measurement of the quality of the components rather than a measurement of charging capability.