they both have to have wheels.
if you do go for wheels make sure that you don’t go for really cheap luggage as the wheels will give you trouble they may even fall apart. get really well made wheels. make sure that the wheels are not to close together. be careful with a wheeled carry on especially if that is your only bag as the wheels will add weight.
sometimes the wheels can make your luggage unbalanced, it will fall over to one side. you will never be able to sit them upright when packed without leaning them against something especially the ones with the big outside pockets. i noticed that more 