Jim,
I don't have all the answers to all your questions and some of the answers really bring up additional questions, but I can offer a little more detailed help.
- I still feel the K-Line models are the least desirable for many reasons. In addition to my previous posts, the master / slave relationship of the units does rely on the lead A unit to run the set and the tether is not very pretty. If the lead unit fails your set is dead in the water. Again, there are prototypical issues I have with it as well. Having said that, I do own a gutted ATSF B unit I picked up for about $20 that I sometimes run in the consist of my EL Capitan set. Using the 5 foot rule it is fine.
- Lionel does not use the K-Line tooling. If you like the Legacy system, these could be a good choice. Buying second hand you can judge color accuracy for yourself. I can't speak to how they are set up in terms of sets as I don't own any modern Lionel diesels.
- Atlas makes excellent models and prior to my ability to obtain 3rd Rail locomotives, they were always my first choice for scale fidelity. Their F units are generally accurate and are good runners. The quality is clear in the slightly higher resale values. These were not required run as sets and you could choose powered or unpowered units as needed. TMCC may or may not be a drawback for you.
- MTH Premier models have come a long way. If you like DCS the recent production models are a solid choice. Up until around 2012 (going from memory here), MTH used a shortened wheelbase on their Blomberg truck which is visually less appealing to my eye. It may not make a difference to you. In short, know what you are buying with used MTH as they are not all equal.
The questions to ask yourself might include:
- What command system am I interested in investing in, if any? Conversely, you may opt to run Legacy and DCS so as to not limit yourself.
- How important is multiple powered units for the layout(s) I plan on operating on? I own with only a few exceptions all powered units as I like to pull long trains. However I have a club that affords that opportunity.
- As already asked, do you have a favorite road? This may lead you in a direction not only for F units, but for future locomotives.
As to the discussion of 3rd Rail product, you can see that there are supporters and detractors. I am personally biased in my support. I consider the product to be mass produced as all the F unit production runs have been in excess of 500 units on the first run.
If I were more objective about it I would say that if you are looking at just F3 or F7 models, then you really can't go wrong between Lionel, Atlas, or MTH. The market has lots options.
Of course with this being the 3RS forum, eliminating the floating pilot and putting a scale coupler on the nose goes a long way towards improving the look of any locomotive.
Hope that truly helps.
