I guess so, but keep in mind groditz can shoot both ground and air, whereas phantoms can only shoot ground.

. . .however, phantoms do a lot of damage to ground & base.  Groditz are only really useful as an anti-air unit, because they can only really kill marines and romans on the ground, and they have much less endurance.  They're close in cost to phantoms, but in the end just can't match up for quality.

Groditz are useful as an anti-air unit?

Last I checked, 5 phantoms vs. 5 groditz... 5 phantoms win.

Groditz are sub-par at anti-ground and sub-par at anti-air. They are a jack of all trades, master of none.

If I was playing outpost, I wouldn't waste resources on groditz, it's quite unfortunate but true, the only useful unit late game for outpost is the hover tank.

I mean, the fact that missiles exist prevents all units besides the hover and queen from being useful (missiles will one shot all outpost units save for hover+queen). And of course, queens are also weak against sakatas and hovers, so they in turn, are made useless as well.

Late game is pretty much a combo of hovers, phantoms, and sakatas. Sakatas are bar none the best anti-air unit in the game. Phantoms are air-based and anti-ground, Hovers are ground-based and anti-ground.

Close cost?

Groditz = 5 + 16 = 21
Phantom = 23 + 5 + 3 = 31

Still though, I'd much rather have phantoms than groditz, even if they less. Also, Groditz do cost 16 manpower, manpower is more important to an outpost player than money is to a forge player. Forge is always a balance between money and energy, if you have excess money, phantoms, if you have excess energy, sakatas. Meanwhile, Hovers eat up manpower for breakfast, so I wouldn't waste manpower on groditz.

Just to make my point on why Groditz aren't as valuable as phantoms in my opinion, I'll list the units that each unit is weak to.

Groditz:
Chronite Tanks
Snipers
Hover Tanks
Black Queens
Phantoms (pound for pound, Phantoms beat Groditz every time)
Gladiators
Sakata Spiders (not that you'd ever use them though)
Missiles

Phantoms:
Black Queens
Scouts
Sakata Mk IIs
Gladiators (kind of... pretty cloes matchup actually)
Missiles

Groditz are only weak to snipers when there's a huge group, they're naturally good against infantry...

Groditz are useful as an anti-air unit?

They destroy scouts pretty easily.  Phantoms, however, cannot be topped by groditz most of the time.

Groditz are only weak to snipers when there's a huge group, they're naturally good against infantry...

Snipers outrange groditz, AND their weapons are anti-chronite.  If you put a few snipers in the hands of a skilled player against some groditz in the hands of a skilled player, the snipers would win every time.

Yeah . . . a glad can kill 1 phantom and die by a 2nd one with no meditecs, so glads win out very slightly.

Groditz really aren't very good overall.  Like Eddy said, they're jack of all trades, master of none.  They aren't really "good" against particularly anything.

Snipers can be microed easily to destroy groditz (or just about anything save for hovers and phantoms).

Eddy is right.

Groditz realy just aren't worth their weight in battle, unless the enemy is building an army of scouts and marines.

Jerry, I, as capitalist, beat you in 1 vs 1 :P
I use capitalist for both outpost and forge.

That's cause i suck in 1 on 1s. Also, if you make buildings faster you'll get the resources before anyone else does. If you make units and structures faster, same thing. You stop your units when you want to and go back to producing earlier than anyone else building at the same rate. (Yes i know you'd have less resources but if you have a sufficient amount it doesn't matter).
I am very tired -_-. 11 pm over here.