It is all about output wattage, they are limited now to 4 watts, some of the early 1960's ones were around 8, you can always add a linear (the pop has one of course) up to 500 watts which is really a lot, I have a 50 watt.
this is what I was wanting to know more of, I found a box of CBs at the farm over the weekend, including a base unit. Was tempted to play with it as I also have a 30 foot tower antenna too