Assuming detached structure since 5/8' is required for firewall and is used in most ceiling apps. BUT they do make a high strength/no sag 1/2" drywall that can be used on ceilings but do a price check in isle 3 before deciding if the no sag 1/2" is worth the extra money vs just using 5/8" LOL!!
Also, for the typical DIY'er, spend the $20-30 on renting a lift, you neck, shoulder, buddies will thank you for it, also get the longest panels you can, 4x12x5/8 is standard product for ceilings and helps cut down on butts you have to finish.
Also, FWIW, do a detailed price break down on steel vs drywall. I know everybody has a "look" they're going after and sometime steel is'nt a look they want, but when you break it all down price wise and labor wise doing steel is VERY enticing:
Steel- looks to be higher inital cost, but they make a thinner panel for interior purposes which is cheaper.
Also look to purchase "Blems" we use "blems/damaged panels" ALOT when finishing off interiors and to date have yet to find the actual reason these panels were put in the ugly duckling pile
When your installing steel-you touch the area ONE TIME and it's done
Drywall-
inital cost at face value is cheaper
now factor in the tape, mud to make it look nice
now factor in the fact your working and going over the ceiling at a minimum of twice, but usually 3 times to get a flaw free ceiling all taped, mudded, and textured
now factor in primer and going over the ceiling yet again
now factor in the paint which breaks down to-
a. paying premium price for a good quality paint from a commercial paint vendor and not that watered down stuff they sell at home centers so you get a smooth 1 coat application
b. buying the cheap home center paint and going back over the ceiling twice to get a nice even coverage so all the work you've done prior is not in vein
drywall you have alot of other materials being purchased to finish it off and typically going over the ceiling, working over your head a minimum of 5 times for a nice looking ceiling...if your standards are much lower and you can live with half azzed work then obviously it's going to cut down on amount of time spent working on it.
Just like trying to compare pole building vs stick built when considering finishing off the interior...the prices even back out and one requires more work then the other.