I have been doing some research on these two tires and find they both are very comparable.
I've read feedback on the Terra Grapplers pulling to one side when in the snow. After looking at the tread design, I can rationalize those comments.
The Open Country A/T's don't have that same tread design. I don't know who makes who but know Toyo and Nitto are affiliated with one another. (I'm guessing Toyo makes Nitto)

My truck has 18" wheels and I'm keeping the stock suspension.
I chose to go with a taller tire than the factory 275/70 series.
I think there is enough room under there but choosing the 285/75 Toyo might be too tall for a stock one ton suspension.

Choosing the Nitto Terra Grappler you get this;

295/70/18
E rated/ 10 ply
16.6" tread depth
34.41" overall dia
11.77 tread
8.5" rim ideal width
4080 lbs
80 psi.
604 revs/mi.

In the Toyo line up you would get this in a comparable size since they don't offer identical sizes in this comparison.

Toyo open country A/T
285/75/18
8.0 rim ideal width
E rated /10ply
66.1 lbs
17/32"
34.8 overall dia.
11.3 width
4080 lbs load
80 psi.

Notes:
The stock Continental TR tires are a 275/70 series and is about 33.1" tall with an 11" width overall.
The Nitto Terra likes a 8.5" rim better.
I believe the factory rim is 8.0"

 

Bench, I'm starting to look into tires myself and am looking at these two tire brands. I just pulled the specs today (weird). Your 350 has a little more clearance than my 250 as it sits a little higher but I'm going to have to do some measurements to see if I'll have clearance issues. My suspension is completely stock. Fortunately, I have a few months to decide. Another concern I have is how easily both tire brands balance. I think I've read the Nittos balance easily but I don't recall reading about the Toyos. If they both come from the same company, then both should have similar characteristics in that department. Gots me some research to do.

 

Subscribed. I've been debating these two tires for a week now. I will say I'm leaning towards the Nitto though. I've read the Toyo's have a weak sidewall that lends to flexing in corners. I've also heard the Toyo's described as "greasy". Only ***** I find in the Nitto's armor is they seem to wear fast if not cared for properly.

 

I am taking a hard look at tires myself SUBSCRIBED

 

I had the Nitto Terra Grapplers 275-65-20 and for the most part I liked them, excellent traction in all conditions, very easy to balance and quiet for an all terrian. But these tires are soft and since my truck is always loaded, I was not comfortable with the feel of the soft tires. I went with the Dura Grapplers for my needs and I am very happy with them. BTW the Terras are still for sale in the classified section.

 

I've run a set of Toyo OC AT's in a 285/75/16 for awhile. I wasn't impressed at all. I also felt they were a soft tire, and didn't perform as well as expected in the snow. I had them when I lived in NH on the side of a small abandoned ski mountain. They were also pretty pricey coming in at $ 1126 installed at a Town Fair Tire.
On the positive side I did manage to squeeze just over 49K in mileage from them. I have been following some of the reviews/comments on the Dura Grappler and since I have no concerns about snow down here I have to read something to convince me otherwise.

 

I'm running the Toyo AT's on my F350. I haul a 35' 14k fifthwheeler about 25% of the time. Great tires. No greasy feel, very solid in the corners. I have 27k miles on them with 2/3 tread left.

They work very well in snow and snow/ice combo.

I will buy again when they need replacement.

 

Toyo boasts in their ad about their 3 ply poly sidewall in their shpeal when you go looking at their tire specs.
But I haven't seen any specs on sidewall construction on the Nitto when looking for specs.

Toyo A/T construction;
3ply poly+2ply steel belt +2ply nylon tread with a 3ply poly sidewall

if you think about it, the Nitto would be the same thing being a 10 ply tire.
But I know what you're talking about because when I went shopping for trailer tires the guy wanted to show me a 10 ply china tire. Right next to it was what I was looking for but an 8 ply and found the 8 ply had a much thicker and stiffer sidewall than the chineezy 10 ply

 

I'm now working on my third set of Toyo A/T's and have no complaints at all about them. They ride great, balance easily, and I've gotten great mileage out of them. They corner as good as you can expect a Super Duty to take a corner, they've never felt 'greasy' or too soft. I don't know about snow but they're an awesome rain tire, I can drive as fast as visibilty will let me in really bad storms and they've never hydroplaned or slid on a corner with me. the only reason I've looked at other tires is because I wanted a more agressive tire. (they aren't cheap as has already been stated.)

 

I am planning on replacing my stock Conti's before winter hits. I've been holding out for the new Nitto Trail Grappler M/T. I have 18" stock wheels on my rig.

New Nitto Trail Grappler M/T...due Sept '09 - Ford Powerstroke Diesel Forum

Any thought's on these tires? I also have intentions of buying a fifth wheel next summer, how do these M/T tires tend to hold up hauling such a load.

 

Update:

I ordered the Nitto's today and the dealer will have them tomorrow. The nitto's are going on my factory lariat rims and will be used for the winter. I stuck with the factory size 275/70R18 and I paid $216 per tire plus mounting and balancing from NTB. I hope to have better luck with them than I'm currently having with the Goodyear Silent armor on my aftermarket wheels.

 

I think they are very similar... the Nittos may be a bit more aggressive than the Toyos.

I run the Nittos in a 295/70R17 on my truck in the winter and like them. They do decent on hard packed snow and pretty good in deep stuff.

 

I misquoted.
Below are correct specs for the factory Conti's;

10.9" tread width
33.4" overall diameter

I seem to be leaning more towards the skinnier tire the Toyo offers in the 295/70.

 

I went with 35 inch Nitto AT's on 18X10 inch wheels on my 2008 F350 SD. I just had to zip tie the fenderwell liner back so the tires do not rub in tight reverse turn. They are just a tiny bit louder than the stock continentals. My buddy has Toyo Muds on his and they are alot louder. The factory lift was enough to clear, and the look is that of a tractor puller with the wide stance.

 

Looking forward to your thoughts

Right now for me it's a toss-up between the Terra Grapplers and the old stand-by BFG AT.