Pregenerated characters vs . Player made characters
The tendency for characters that are made ahead of time, usually called pre-generated characters, is that they are made for shorter sessions and not for campaigns.
Pregenerated characters are when the dungeon master arrives with characters prepared ahead of time and are mostly used for one-shot sessions and if you are headed into a roleplaying con you want everything ready in advance.
The point is it saves time since usually one-shots and cons are one evening or one afternoon affairs and the table cannot afford the players spending 1-2 hours making their own characters. It is very handy in those situations.
For modules that span more than one evening or campaigns, a more common practice is to allow the players the freedom to create their own characters so they can flesh them out more. Then they can spend more time picking out the race and class combo, figuring out their backstory and perhaps why the hell they are out adventuring instead of being a farmer or a blacksmith in their hometown.
How about letting the Game Master work his magic ?
Game masters or dungeon masters, whatever you may call them, plan the first evening of a longer session to get the players to make their character. It can depend on the setting but for myself I usually allow the players as much freedom as they want but try to stay within reason. Sometimes I will allow experiments to see how things play out but most of the time we have some boundaries to make sure the game does not go out of hand in terms of power playing. We are not really here to talk about the actual character creation itself but the choice between letting the player make his character or the game master.
Now the concepts are obviously not very complicated so why are we discussing this ? Because perhaps you would like to use pre-generated characters for a longer session or a big campaign. Perhaps you have been wondering what your players would do if you put them in unusual roles or have them do something they are not used to. Shake them out of their comfort zone if you will. I decided to try it out once and it came out relatively well. I was imagining a lot more backlash since I was effectively stripping the players of one of the fundamental ideals in this game, their freedom. It turned out that they were all ready to have a go at this and ended up having loads of fun with their new characters. Our group rotates somewhat who is the game master so others had a go at this as well, with a bit more freedom than I did and that also worked out pretty nicely.
The reason we decided to do this was to shake up the roles players usually picked and do a little switcheroo. The rogue got to play a paladin, the wizard played a ranger and the fighter was sent skulking into the corners and the barbarian had to throw spells out.
This is, however, not something you should do too much of because this will limit the freedom players have and while it worked out for our group, there are groups out there that will not have any of this. It worked because our group was open-minded enough to trust the game master to pick out races and classes for them. After the initial character creation players could of course go whatever route they wanted and if their characters happened to be killed off, which is not something that happens too often, they were allowed to pick entirely new ones.
What this did for our group was to encourage players to go outside of their comfort zone and try new things out. When I am a player I tend to lean on playing a fighting type character that is usually more nimble and rogue-ish rather than playing wizards or clerics and in one instance I was set to play a cleric. It was a lot of fun and my friend who usually plays a rogue played a wizard and we managed to make a really fun combo with those two.
If your group is not entirely against this idea it can be fun to see where it leads and how players respond to having their characters created for them. It could perhaps get them to play a more diverse set of characters in the future or they could like the change but will go back to their usual character. Neither option is a bad thing but at least they get to experiment with different roles and hopefully enjoyed the time they spent doing something else than their usual schtick.
While this can be a good idea to spice things up and take your players out of the comfort zone you must be careful about talking with your group beforehand or you could land in a situation where your players can feel like you are playing the game for them and that can lead to railroading arguments.
The bottomline is always do what feels best but do not be afraid to talk to your group and see if they would like to try new things out and have a pregen character for them and to what level you can do that. Are you just picking out the class and/or race or are you going to go all the way and roll the stats, pick the feats and assign the skills. For myself I always like to have a small degree of freedom even in pre-generated characters for my long time campaigns. This can be different for groups but some groups have no interest in letting others assign characters to them and that is perfectly fine as well since the main thing is that everyone has fun.
Remember. It is all about having fun
Having a pre-generated character means you can start the show a lot faster but also hampers the freedom players have and can mean they will feel more detached from the character and think of it more like stats on a piece of paper than an actual character. For a veteran player that always sticks to the same role throughout the years this can shake things up. For new players it can be good to have some ready made characters on hand to give them if they are unsure how to act. It can also be good to have some characters ready should a player lose his character in an untimely demise. It all depends on the group setup. The key thing is to have fun. It is a game after all.