MTH PREMIER,RAIL KING differences

I know of only one Premier line. Railking has 3 lines in their current products.

Premier is scale (1:48 size), highly detailed and is their top of the line product. Usually require larger curves. Purple boxes.

Railking is a lower cost line with 3 different catagories. Requires smaller curves, usually O-31. Mostly Yellow boxes.

1. Railking Scale line (also 1:48 size) that is much less detailed than the Premier line. (I am not certain on this but some of the RK Scale engines may require larger than O-31 curves?)

2. Railking Imperial, slightly smaller than scale 1:48 size, but highly detailed.

3. Railking is smaller than scale and not as detailed as the Imperial line.

PS2 and PS3 is the same across all lines, but the Premier versions sometimes have more features than the Railking items.

To answer your question:

• All of the PS3 (and before that PS2) electronics are the same across all of MTH's product lines, both Rail King and Premier
• Premier models are more expensive than Rail King models
• Premier engines are all scaled-sized and often require larger diameter curves than do their Rail King counterparts
• All Rail King engines can negotiate O31 diameter curves
• Rail King Scale engines are scale-sized, however, they are not nearly as detailed as their Premier siblings. All other Rail King engines are not scale-sized
• Rail King Imperial engines, while not scale-sized, are selectively compressed and make a very nice appearance. Further, they have more details and may have more features than do other Rail King engines
• Rail King engines without a suffix are somewhat lower on details and have a pretty much standard set of features
• Rail King Rugged Rails have the least detail and the fewest features, and are typically found in lower-end Ready To Run starter sets
• Price-wise, from high to low, they stack up as: Premier, Rail King Imperial, Rail King Scale, Rail King, and Rail King Rugged Rails.

The differences between the two particular engines that you're comparing. the Triplex Premier and Rail King Imperial models, can be summarized as follows:

• Premier is scale and Imperial is not
• Premier requires O72 and Imperial requires O31
• Premier has a smoke unit in the tender and the Imperial's tender has a dummy smoke stack
• Premier (latest PS3 version) has a Playable Whistle and the Imperial does not
• Premier has more detail than does the Imperial, however, the Imperial has quite a bit of detail, as well (real coal load, tender chains, firebox glow, marker lights, interior light). 

I own the first PS2 3 volt Rail King Imperial Erie Triplex and it's one of my favorite engines.

Much thanks for the info , I appreciate it very much as usual.

Jerry