In GU there's a higher need for material gathering during hunts and item preparation before hunts. Rise took away the need for cold and hot drinks. Whether or not that was a valid quality of life change, it is a necessity to keep in mind in certain maps in GU. Whetstones, bugnets, and pick axes also break.
Combat has more emphasis on animation commitment, timing, and placement. GU has a certain turn based sort of rhythm in combat. Punishment for breaking the rhythm is higher since there aren't wirebugs to gain distance after getting slammed. I haven't played in a year, but I do remember fights lasting longer than Rise. Some can go on for 20-40 minutes the first time you face a new monster. There are a lot more monsters in GU than Sunbreak. It looks like GU has 93 large monsters vs Rise with 46, Sunbreak with 27, so 73 total. One criticism I've read about GU is the pacing and lack of story. Since it's a generational celebration and there are so many monsters, you don't get the handpicked progression of power that's present in older titles. Rise has a more coherent story, with monsters relevant to it's progression. They missed out bringing back a few monsters, but overall Rise Sunbreak's roster is really strong. With GUs monster roster and weapon skills, there are so many monster vs weapon/skill matchups to master that you basically have near endless content.
Another difference between games is that GU has the old school map areas that you load into, meaning you can get juggled out of the area you're hit multiple times near the edge of the map. I've been juggled out of the area from multiple hits on high rank monsters a few times. It's kind of cheesy, but it gives you a moment to heal or sharpen if needed. In Rise you can wirebug to a higher area or ride your palamute to do the same, so it's different implementation of refreshing mid battle.
GU was my first view into aspects of the old school Monster Hunter games. After playing 150 hours it solidified Monster Hunter as my favorite game franchise.