This is the quick, cheat-sheet on some of the armor specifics that I've gathered over the years. But the devil is in the details, which can quickly derail any thread. There are also many sanctioned recasts being sold under other names.
TE, TE2
This is where original, screen accurate armor and helmets supposedly originated from. However, both Gino and TE have continued for years to claim authenticity. TE has since sold his molds and the new owner is going by the term TE2. This armor historically has been considered the most accurate, but know that it has been modified and has many differences (pro or con) from other similar armor. A few differences are the shoulder bell 'swoops', the flat ab plate, unique left bicept and right arm, but most importantly, it has correct-looking, shin armor unique to each leg. The more common AP armor does not have this. This armor has historically been made in a thin gauge of HIPS plastic, and is not suitable for repeated, long-term trooping. I have two of these kits and they require numerous fixes over time.
Gino
Another armor maker who claims to have the original molds but has not modified them unlike TE. However, his helmets and assembly skills are some of the best, being made from a combination of two original, screen used helmets from ANH. Not as readily available as other options here, but probably one of the best.
AP (aka Authenticprops)
This armor orginated under the GF name, which originated as copies of TE's (or Gino's?) molds. They have since been resold and are now available under the Authenticprops name. It is currently made in .80 ABS plastic and includes everything nessasary to complete assembly. I've assembled a few of these sets and noticed that both arms are the same and the inner right leg is the same as the outer left leg. Because it's also being pulled in ABS, the detail is not as sharp as the pulls from a TE2. Regardless, it's probably the best alternative for those seeking a relatively accurate suit of armor that's durable enough for repeated trooping.
RT-Mod
Fan made armor with a very good likeness to the original ANH style. Made of a heavy gauge .90 ABS. Great alternative to the more typical FX armor.
FX/GT
The most common armor available, all over ebay and resold on numerous web sites. Most anything being sold for around $500 to $600 is a FX kit. Made of .90 ABS plastic, looks good for what it is, which is a fan sculpt but not accurate at all. 90% of all 501st members wear this type of armor. The helmet is notorious for it's over-sized, bobble-head look.
Movie FX
Based in Germany, this is another common armor vender who's name comes up in conversation a lot. In short, if you live in the States - don't even think about it. Almost everyone who's placed an order never got their stuff. The origins of his newest armor and helmet are up for debate.
AA/SDS - Original Maker
Andrew Ainsworth of Shepperton Design Studios, the original fabricator of the Stormtrooper armor seen in the films is offereing helmets and armor claimed to be from the original molds. Many believe his claims to be dubious and evidence suggests such. While his helmets may indeed be from original molds, by his own admission they have been modified since originally used in the 70s. His armor is also most likely a recast of a TE or AP suit. Ironic that the original maker is recasting someone's recast of his stuff. Be aware that he is also facing legal charges and litigation with LFL for selling these unlicensed props.
TM (Troopermaster)
My new hero. A 100% fan sculpt but probably the most accurate armor in the world (for not having been recast from screen-used items). True dedication from this amazingly talented artist has produced some of the nicest armor I've ever seen. A true trooper master in every sense of the word.
