I have purchased two 0-10-0 locomotives, the blue Chloe, a small orange German v10 switcher, the Lehmann, sugar company, Porter, and the Nevada, Central Mogul, 2 SOEG 0-4-4-0, 3 SACHSEN 0-6-0 KII, a Spreewald, frr diesel, and more than 20 freight and passenger cars.
I have a lot of the old LGB equipment (an embarrassment of riches) so I am well-versed in being able to compare old to new.
I think the quality of the marklin made LGB is virtually the same. One thing I can say, having several of the old Chloe‘s, FeldBahn steam and diesel, and Olomanos is that the new “transmission“ is only a slight improvement over the original belt version. As noted by several above posts, Unfortunately, only one axle is driven by the motor worm gear. As on the originals, overloading the locomotive will wear out the axle gear. Also these locomotives have a small motor that runs hot regardless of load, incline, or other factors this limits, my running of this type of locomotive to about 20 or 30 minutes tops. Otoh, i notice no difference in noise. Simply, these locos are deserving of more care than typical lgb. I keep the skates despite the drag, as they hugely reduce micro arcing and pitting of the wheels.
While I find the new LGB paint schemes to be more realistic, I also find some of the detail parts, a bit more delicate and prone to loss, eg Heberlien brake stuff, whistles. Marklin does not glue these parts in the way that LGB did. I have also found, on very similar units, such as the.0-10-0 locomotives, one may have the gauges painted with dials, and the others on another locomotive are left blank. I don’t know how certain features are “priced“. A newer locomotive will have more MFX sounds an older version fewer, but perhaps more detailed and complex paint schemes.
Now that I am using the marklin cs3, I find more value in the MFX equipped locomotives. I am a digital idiot, so the central station helps me operate without really understanding how to assign addresses or reprogram CVs. Im sure most here are digital, but i was slow to adopt. Sure makes operations a lot more fun.
Again, I think the quality is every bit as good. Value, on the other hand is in the eye of the beholder. Many Cars are now at least $200+, ouch.
As I am retired, I am more and more put off by the $2000 plus versions. Especially now that obtaining LGB spare parts has become far more difficult, for some items.
Otoh, i still get a thrill from a ‘new train’, lol. And, ones that last and run without much tinkering.