GRJ's analogy of Mercedes vs. Chevy is a good one, especially if one considers the total cost, not just the locomotive and system costs. As others pointed out, Legacy is only available in 1:48 scale engines which are, of course, more expensive. More to the point, so are the 1:48, more-detailed scale passenger and freight cars that match the engines, just like the parts and maintenance costs with a Mercedes are reportedly higher than the Chevy. You pay for performance upfront and on-going.
LC+ and LC+2 comes in semi-scale and some scale-sized locos but appears to be generally geared to the simpler and lower-cost market relative to Legacy. They match nicely with traditional/O27/O31-sized rolling stock that are plentiful, less-detailed, and lower cost.
So relative total cost should enter into the discussion along with space. Legacy engines and rolling stock require larger curves and more space and more money.
Also, consider quantity. Will you be satisfied with 2 or 3 engines or will you become addicted and need 20? Will one set of passenger cars be sufficient or will you get the bug and need six?
If you have the space and budget, 1:48 scale with Legacy is the way to go. If budget, space, or tech skills are limited, LC+ and its upgrade LC+2 seem like a better option.
Plain old LC is for entry-level toys like my youngest's Thomas set. Nothing wrong with it. In fact, as a 4 y/o, she loved it.
