people will hate you for playing 24s but imo it is better than 29s since there are just hunters and rogues with GF'd weapons that hit like trucks.
But i say roll 24.
Pros:
More gear options. No certain "Bis" list.
Access to Gnomeregan items.
More abilities than a 20.
Cons:
You will be hated.
"Stat scaling is less"(put in quotations because you get more gear and iLvL 29 items that give more stats than what is available to a 20)
There aren't any true bad things with 24s just do this:
Don't be bad.
Don't Gy farm/ MF farm.
Kill bad hunters.
Cap flags/ return flags.
Help the truly newbie players.
Do the above you will be good. i do that on all my 24 characters.