One the things I’ve noticed as I play more and more 5th edition D&D is that the changes to the action economy have a huge impact on the way the combat encounters play out. I can’t help comparing it to the 3.5 edition campaigns I run and play in. Overall, they’re very similar, sharing the same major points. Beyond that, the similarities start to break apart and each version tends toward the overall design patterns of each system. 5th edition tends toward simpler types of actions and broader classification while 3.5 tends toward greater variety but a rather extreme degree of complication required to access that greater variety.
In 5th edition, there are four types of actions a player can take in a single round (the time it takes for all characters and monsters in an encounter to take their individual turns): A “movement,” an “action,” a “bonus action,” and a “reaction.” There are also “free actions” but those are given at the DM’s discretion and can be used for saying something brief or certain skill checks depending on the DM’s decisions. A “movement” is exactly what it sounds like, plus a few other things. Your character can move up to their maximum per-term distance or do some sort of movement based action like standing up, climbing, jumping, or dropping to the ground. An “action” is a very broad classification encompassing everything from attacking other people to casting spells to interacting with other people or the environment. A “bonus action” can only be used as a result of a power granted to your character by their class or by a magic item. This can be any other classification of action, but only a specific action per power. For instance, a rogue gets a bonus action that lets them run away from enemies during combat or hide themselves after attacking. The last type of action is a “reaction” and that is a very specific subset actions that can be granted by your class or are one of a small set available to all characters: counterattacks as enemies pass you, cast certain spells, or use an action you prepared.
During the early levels of a 5e game, most characters use only movements and actions, occasionally dipping into reactions. At higher levels, most characters have a variety of bonus actions to pick from and sometimes ever class abilities or spells that give them additional actions. This keeps combat encounters moving relatively quickly for early levels but can bog down combat a bit at later levels. An added complication at later levels is the introduction of “legendary actions.” These are actions available to a certain class of powerful monster, typically used as boss monsters, that give them additional actions they can take when it isn’t their turn. This can help offset the ability for a group of high-level characters to gang up on a single monster and destroying it before it can do anything because they have so many actions they can collectively take each round. That way a legendary monster is attacking the characters just as many times as they are attacking it.
In 3.5, there are a greater variety of actions. There are “full-round actions,” “free actions” (that function the same as the 5e classification of the same name), “standard actions,” “move actions,” “swift actions,” “immediate actions,” and the dubious titled “no action.” “Move actions” and “standard actions” are basically the same as 5th edition’s “movement” and “action” classifications. A “swift action” is similar to a reaction, but on your turn. It is used for certain types of spells or activating certain magic items. An “immediate action” is a specific subset of “swift actions” that can be used at any time, even when it isn’t your turn. The “no action” is used for minor shifts of footing (like turning in the space you already occupy) or for delaying your entire turn until a different time. The “full-round action” is a type of action that uses all of your other actions at once to do something big like cast a difficult spell or perform a few attacks at once.
From almost the very first levels of 3.5, characters have access to things that use all of their action types. While the number of things they can do with these actions is limited, a clever player can find a way to put them all to use. As the players level up, the opportunities provided by all of these actions only increases. The only thing preventing individual turns at later levels from lasting forever is how difficult it can be to parse through the actions available to a character and which actions are used by what abilities. The rules are often open to interpretation or buried deep in a seemingly unrelated section. The balance is that since most people can’t figure out how to exploit the action variety in 3.5, it usually never becomes a problem. While certain monsters can make use the variety of actions available, most cannot. Without legendary actions, most big, solo monsters are at even more of a risk than their 5e counterparts because they only get to attack once their turn and can be quickly killed before they have a chance to attack plenty of people. 3.5 counters this somewhat by giving solo monsters abilities to damage lots of people or have a chance to take people out of the fight temporarily.
As a DM, I prefer the simpler 5e action economy. Each action is its own thing and cannot be turned into a different action type. In 3.5, there is an action hierarchy and bigger actions can be used to get an extra action of a smaller type. A standard action can become any other kind of action, while a move action can become a swift action or immediate action. This means that a lot of tracking needs to happen so I can make sure my players aren’t abusing the system by taking multiple swift actions when they shouldn’t be able to do so. The action economy gets incredibly complicated once people start trading actions around or using abilities to change things so that something that’s usually a standard action now happens twice as a swift action.
The longer I play 5th edition, the more I consider swapping to use only that system. I’d miss the variety and options I have in 3.5, but it would make my individual sessions much easier to run. I’ll probably never leave 3.5 because I want to tell a good story more than anything, but I can dream.