First off, all of the objections you raise seem to be for older Lionel locomotives that don't have cruise control. My Legacy diesels start moving at speed step one, and they move very slow. DCS locomotives are only guaranteed to run smoothly at 5 scale MPH or more, however they typically do considerably better. While DCS is good at low speed, I think the Legacy stuff has the edge at very slow speeds.
You need to be specific as to the exact makes/models you're comparing as your descriptions don't match my observations. My legacy locomotives at speed step 15 (out of 200 possible speed steps), are still poking along, they're running very smoothly.
Yardmaster96 posted:Lionel doesn't kick in until 8 or 9 on the mph meter, where MTH almost moves at 1.Once Lionel is going, you can dial back to 4 and that's creep mode. But it won't move at all when you first dial in 4. What gives?
This is not normal for any locomotive with cruise control, so either you have one without cruise, cruise is switched off, or your engine is broken.
Yardmaster96 posted:I like certain features of both. I especially like how MTH engines have that engine RPM increase whine, but I do have to drop the volume on the DDA40 because it's like standing next to a jet engine. I know, I used to crew Blackhawk's. I like how Lionel's engines say, "that's if for us dispatcher, we're going to the house". MTH just powers down quietly and goes silent. Lionel's also go into panic mode if you shut down with any mph left on the scale other than 0. It's cute after you know why, but hat first time can be a shock to the system because your initial response is, "what the hell did I do!"
Legacy diesels have all the sound features you're talking about. In addition, you can do a ton of neat audio tricks with the Legacy CAB2 in conjunction with a Legacy locomotive. Increased labor sounds, etc. are all at your fingertips.
FWIW, you can have a Legacy engine either have the shutdown crew talk or just have it do the shutdown sequence without any talking, depends on which button you push.
Bottom like? You just need to spend more time learning how the two systems work before getting worked up about capabilities they do or do not have. 
