One of the most complained about things in Halo Reach are the armor abilities. It just so happen the people who typically complain about armor abilities praise everything about Halo 3. They seem to forget just how broken the equipment was in halo 3.
Bubble shield: at close range its nearly useless because people can run right through it and continue to kill you unless you had a shotgun. At long range it takes at least a second for it to deploy. so when your shields go down and you know you need a bubble shield, you toss it only to die and it opens on your dead body. saving you from rockets, banshee bombs, etc. was out of the question because of how long it took to deploy.
Power drain: at long range it takes forever to deploy and reach the target and by the time it does your own shields are already down and its as if you never had it in the first place. or if you were at close range most of the time it ends up hitting you somehow and draining your shields with the enemy
Flare: one of the dumbest equipment in the game. It blinds you in the process of throwing it and is hardly effective. I only remember this on guardian for a short time before it was completely removed from MM because of how broken it was.
Radar jammer: this was also useless because it made your radar jammed as well so deploying it gave no advantage. I also believe this was completely removed from MM because of how broken it was.
Land mine: no one is going to be stupid enough to walk/drive over a big glowing flashing beeping land mine. so the only way to ever get a kill with it was to deploy it a fraction of a second before you got splattered by a vehicle. only problem is, it wasnt powerful enough to kill a warthog at full health. this made it almost completely useless considering most warthogs and ghosts tried to gun you down as oppose to splatter.
gravity lift: Probably the most useful equipment in the game. it had a simple job and it did it well. the only problem with it is if you put it in a bad position you couldnt adjust it after being deployed.
regenerator: Almost every time this was used it turned into two people in a beat down contest where the winner seemed to always be random. it was only usefull to use if you had a shotgun or sword and the enemy didnt.
so there you go. out of all the equipment in halo 3, only one was usefull and did its job fine. and two were completely broken and were removed from MM. nearly all of them slowed down halo 3's already slow paced gameplay.
meanwhile in halo reach. the only armor ability thats broken is armor lock. the rest do their job fine and dont slow down gameplay like the equipment in halo 3.