Carl;
I have a TJM on my 7.3 Ford. I would suggest not getting a snorkel at all, but if you are determined to get one, then go with the TJM.
Here is a pic of the Safari/ARB:
The Safari Ford 7.3 model has a weird molded one piece head that wraps along the roof, and in my, admittedly very biased, opinion is rather ugly.
Here is the Airtec/TJM: It has a more traditional head design that would allow a prefilter to be attached if desired. In my opinion it is a little better looking than the goofy Safari design.
I only have experience with the TJM, but I would think that most of these comments would apply to both types:
Disadvantages:
1) The tube runs up the drivers side A pillar and restricts vision slightly, but is a real problem in a heavy snow fall. Driving in heavy wet snow means that the wiper piles snow and ice up against the A pillar tube until it becomes so bad that the wiper travel and vision are seriously restricted, meaning you have to pull over and brush and scoop the accumulated slush away.
2) The big diesels need a lot of air, and the snorkel definitely restricts the amount of air getting to the engine. The opening at the head of the snorkel is similar in size to the oem intake, but the long curved tube adds a lot of restriction, for this reason it is also quite noisy.
3) For some reason the sight of a snorkle on a large pickup provokes endless amounts of questions, comments and even rude jestures! This can be fun when you are in the mood but can get a bit tiresome if you are not.
Advantages:
I assume you know these already or you would not be planning on a snorkle.
1) Protection from water ingestion. I fitted mine for my trip around Oz, due to the number of unavoidable creek crossings that can vary in depth dramatically depending on the weather. However I learned a trick over there that seems to work well. Even when crossing creeks that are deeper than the height of your oem intake, a simple tarp can be used to form an air pocket and protect the intake.
2) Reduction of dust in intake. I don't think this makes much difference if you travel solo most of the time. I can only see an advantage when operating in extremely dusty conditions while following other traffic.
For what its worth, that is my snorkle sermon
Cheers
Mark