Hi Bmann! Welcome to the forum!
You are comparing the ST 1400 to the SI Model 3: A little bit "apples and oranges." I say this because of the size and capacity. The 1400 is much more comparable in size to the Model 2 (1400 has 14.5" x 14.5" shelves, and the Model 2 has 15" x 15" shelves. The Model 3 shelves are 15" x 20": that means you can easily fit a full packer-cut brisket in there; can't do that in a 1400.
Heating elements: The 1400 has a 700w element, same as the Model 2. The Model 3 is 1200 watts - big difference.
All stainless steel construction in both brands, same amount of insulation. Many of us have smoked in sub-zero temps with no problems. Check out some of the cold weather use posts, there are lots of them. Also, the inside and smoke boxes are virtually identical between the 2 brands.
Door latches: These types of smokers use a compression-fit door (no gasket). The latch(es) actually compress the door against the frame to seal it. The 1400 has one latch (insufficient, in my opinion, for that size door). One is fine on the Model 1, but not the Model 2 or 3; that's why there are 2 latches on the Model 2 and 3. Seals the door much better.
Wheels: The 1400 has small wheels, whereas all the Smokin-It models have larger, heavy-duty castors, 2 locking. May seem like a small thing, but makes a big difference when moving the smoker.
"Set and forget:" Yes! The SI units are absolutely set and forget! If you spend much time reading through the boards here, you will see that reinforced many, many times! They work exactly the same as the ST models!
Here's my opinion on what makes this such an easy decision:
Price: The 1400 is showing $595 on the ST website. You can get a Model 2 for $399. Almost $200 cheaper for the same size smoker. If you need the capacity, the Model 3 is still $100 cheaper, and a whole lot bigger! No brainer.
Warranty: ST has 2 years, SI has a 3 year warranty.
Customer Service: You absolutely will not find better customer service than with Smokin-It! When you call "customer support," you get a guy named Steve, who just happens to be the owner of the company! That doesn't happen very often! I can also personally endorse the service you will receive, and tell you that you won't find a finer group of people to deal with. Steve will bend over backwards to keep a customer happy.
Bottom line? I did the same research when I bought my Model 1 a year ago, and am so glad I made the decision I did. The reason you are finding many more reviews for the STs is they've been around longer. SI is hands-down more value for the dollar, and I believe has several improvements over the ST models, and is still cheaper (less-expensive, that is)!
Hope this helps - feel free to hit us with more questions, and look at the satisfied owners posts here. We have added about 400 members in the last year, which is pretty impressive, in my opinion! This forum is fast becoming the premiere "manufacturer's" forum on the web, built by satisfied owners. Hope to see you join the family! 8)
edit: I realized I said there were 3 latches on the #3; there are 2.