The Legion, Fiend, or Gibson dog?

I don't know how much the attack value increases with the Gibson dog so I don't know whether it will be better than the extra hit points. The Fiend speed upgrade sounds nice but if it just effects movement speed its useless as it will just allow the dog to run more quickly to its death.

Bonuses for each dog are different.
Old Lady Gibson's dog, Rey: improved attack, a Guard dog.
Violetta: the fiend dog, increased speed, chems.
Lupa: INcreased hit points

Data on the Wiki readout of the quest http://fallout.wikia.com/wiki/Nothin%27_But_a_Hound_Dog

I didn't vote because I haven't tried all the options. I will say this, though:

NOT Violet's dog. The only thing worse than a weak, easily-killed Rex is a weak, easily-killed Rex who plunges into impossible odds even more quickly...

Gibson's dog definitely gave a noticeable increase to attack, but I still felt like Rex lacked durability.

Gibson's dog. I'd rather have a higher damage Rex so he'll do a little more before he falls over unconscious. But in this game, extra HP's do make quite a bit of difference for companions in most scenarios, and 100 is a lot. He has 8END.

If you're on core then gibsons is great. hardcoe i went with lupas? ( the one that gives him armor). Figured cazadore hunting + rex = dog meat so armor was the best choice.

There is no NCR Dog to put a brain in Rex, its just Fiend, Legion, or Gibson Dog.
But Gibson Dog is the best to implant in Rex.

Went with the Gibson Dog just because I thought if I went with the other dogs REX would end up going evil-crazy or something. Only after did I realise the doc tells you what each benefit is

I was thinking replace Rex's head with ED-E....

I prefer ED-E. Any NPC that comes with it's own bumper sticker is a freind of mine.

Actually, occasionally a dead NCR guard dog will have a brain you can take. There's no benefit to Rex though (other than a new brain).

Has anyone tried using Moe's brain?

None. Put Rex out of his misery.

Cyberdog. Sheesh. <_<

Gibson's for me, since I don't really use Rex, I rather him to have a brain from a "nice" dog to live peacefully ish than the other two options.

I really dislike the cyber dog's look, I much rather the NCR guardogs.

I use the lupa's witch is the legion's dog. Rex witch is at gibson scrap yard gives incereased attack damage,Violetta is the one near the poseidon gas staion on the outskirts of west new vegas that dog gives you increased movement speed and lupas witch is the legions dog gives increaed toughness.i had rex with that brain for awhile and hes pretty good also i belive toughness is is all those benefits together pretty much

I play on hardcoe so Lupa's hitpoint increase is a more welcome benefit. The only problem is that I did not see a huge difference to Rex's durability as I did with ED-E, when taking the machine to the Brotherhood for an armor upgrade.