ok I will chim in as I have started threads about this subject and posted in many too. I use these few rules in order to build what I think is a very quailty cage.
1= safety for my family
2= purpose of the rig
3= weight of the rig, IE: fully loaded with people, fuel, gear, etc
4= survivability of a BAD roll, cage design is CRITICAL HERE
5= low maintenence
1 safety= nothing is more important then my family. so keeping them safe is paramount and superceeds all. yes on hard core runs my family might not even go, probably just a guy trip but if they do I want my rig as safe as possible.
2 purpose of rig= I am building a hard core capable trail rig that still will be street legal (realitivly legal

) if I never use it to its capibility so what, but I plan on it, so a bad roll will be inevatable at some point.
3 weight= probably in the 6000+ lb range.
4 survivabilty AND design= I will build it to handle a BAD roll over, wheather it be a hard flop to a multiple roll. most tires up are just soft flops on the side but multi rolls happen when you dont expect it....then its too late to go back and build a better cage.
5 low maintence= I dont want to have to section tubes out or atleast not as often as I would using lesser quality tube/pipe.
My personal choice is nothing less then DOM period. I dont care about cost. yes it IS very expensive but it is what it is. I would take a pipe cage ANY DAY OF THE WEEK over nothing at all if I was going to go wheelin, especially on a tough trail.
on a budget the minimum should be HREW. if you cant get it at the local steel place, save some more money to pay for shipping, order it and have it delivered.
CROMOLY cages are for the high end racing rock rigs or baja type trucks. if you can afford it and can weld it properly, have at it but I cant.
I prefer to build overkill, I dont like to build what is probably suficient, I want to KNOW its going to hold up to those "not intended for incidents" so for me its 1026 DOM. for my trail rig.
for my daily driver and some times off roaded suburban it will be HREW since it wont see the kinda of trails my blazer will see.