My 2 Copper Pieces:
I have looked into GURPS and while the 1-second round/realism is tempting, I also found it constraining and actually unrealistic. The lack of time inhibits many things I believe, primarily being able to keep track of the fight going on around you, but also the full-defense action being able to be taken alongside the attack (or whatever) action. I think that you need a minimum of 2-seconds to all of that, with only those highly skilled and experienced fighters being able to go beyond that and add in extra attacks. (Or other actions, like maneuvering.) A longer combat round allows us to emulate different levels of ability better, as well, to reflect those times when highly-skilled combatants are fighting alongside (or against, or both) novices.
Also, I believe a little abstraction is needed to help the GM and players in using their imaginations to come together and describe how things went down in any particular combat round. With the uber-detailed 1-second combat round that is much, much harder to do, to the point of being nigh-impossible.
The very short combat round also requires re-training for the players (and GM) who are all used to doing something each and every round. This re-training, I feel, is unnecessary and too difficult to be bothered with. (I have tried it on a couple of groups now, comprised of both old-school gamers and newer gamers, and neither liked it; it is just simpler to stick with what they know in this regard.)
It is unrealistic in the sense that the only thing to go on in a combat round is not an attack, or more specifically, each attack isn’t just a sword thrust or pulling the trigger of a gun. There is movement & looking for advantage as well as trying to keep an eye on the fight going on around you so someone – or something – doesn’t get up behind you. Watch both MMA fights and movies and TV shows with lots of actions, both show lots of time taken up by the combatants to maneuver both defensively and offensively. The MMA fighters don’t just stand toe-to-toe swinging at each other, and the cops & robbers don’t just stand in the middle of the street shooting at each other. (While the latter is obviously fiction that does tend to be the stuff we are trying to emulate, so it pertains here. Plus, modern TV & Film making has gone to great lengths to make some things look real – though others are obviously far-fetched for entertainment purposes.)
My preferred combat round length: 5-6 seconds. I feel that gives me just about the best length of time to emulate all of those things that go into a single combat round. Also, I don’t like an arbitrary Initiative roll made up of some purely randomizing elements that is barely connected at all to the character in question. I believe that to gain initiative in the combat round you need to be more aware of what is going on than your opponent(s). This is why I prefer a combat perception test over just 2d10+Qu Mod. Then, you go from lowest to highest in calling actions, but perform them from highest to lowest initiative totals.
One thing I don’t like is the whole “I got initiative, so I move 30-feet and attack, before my opponent can do anything at all” scenario, that tends to permeate longer combat rounds. I like to have actions take time, so if you have to move then attack, your movement might come before your opponents attack (or other action), but your attack may not. I say “may” because if I feel – as the GM – that if the PCs initiative score was high enough over their opponents, I might say they can do both before their opponent does anything. With a 5-6 second long combat round I can abstract it enough to do this, while the 1 or 2-second combat round tends to take this out of the GMs hands. (I am firm believer that there is a GM for a reason, otherwise I would be playing a video game.)
