Ohhh, interesting. There are a bunch of groups here in SoCal, but I've yet to connect with any of them as I'm still getting myself sorted and making sure I have the minimum gear necessary to join. I'm also more interested in overlanding than "off roading" or 4x4 culture (it's about getting to places I couldn't otherwise see, not seeing if I can make it from A to B for the sake of making it); some of the groups here seem to be about the hardcore 4x4 life.
I honestly don't know much about the differences. I don't mind paying $70 for the license, I just don't have time to deal with studying and taking the test for HAM certification. Work is too busy for that. Do you have a link with more info on how to deal with the GMRS license?
IMO these are very different animals. Having spent decades doing both overlanding (as it's now called) and on hardcore 4x4 trail runs this is my take on it.
As an overlander you're looking at covering large distances over varying amounts of time from days to weeks or even years, often alone, while 4x4 clubs are looking to find a challenging trail that might take a day to several days to run then returning home.
If you're looking to get into overlanding then ham is the way to go. Ham offers the next best way to summon help in the back country or even along roads with little to no traffic to help should you break down. Also it gives you the best of long range comms by using repeaters or even HF to summon help. You'll find a lot of 4x4 clubs also use ham or will have several members with ham radios you can talk with if you're with a club. Plus the USA has agreements with many other nations around the world that will allow you to use your radio in their country with little to nothing to add. And as already covered you can buy a cheap GMRS handheld radio and get the license if the club you join is GMRS only.
If you're looking primarily to go on runs with clubs or groups that take days to maybe a week or two to complete then join the club and find out what they use and follow along. You might not even need a GMRS license if you just want to listen but you'll find that kind of sucks for more then a run or two. Or they might be one of the holdouts that still use CB.
GMRS, CB and most other of these types of comms are primarily U.S. only (not sure if either are allowed in Canada) and I've read where some countries will even impound them if you try to bring them in.
The next best thing to the above would be one of the systems like Spot or InReach, particularly if you'll be traveling alone or with just your family in very remote places then while expensive it might be your best option. Not cheap but your life is worth it!