[Snowflakian]

ML is great for collectors.

For kids and collectors though, MU is better. (Not saying collectors shouldn't buy ML, to each their own, just pointing out some key factors why MU is better for kids and collectors with limited space.)
You've got cross pollination of lines because kids do that anyway. You've got vehicles that take up about as much space as two ML figures but cost less. You've got GI joe shield bolsering that can help expand how kids play or collectors display.

On top of it all, let's look at the average parent. You've got 100 bucks to spend on your kid for marvel stuff in the winter holiday season.

Do you:
A. get them as much MU as you can which is anywhere from 10-13 figures.
B. Get them 6 maybe 7 ML figures.

I don't know about you, but A. seems more lucrative. Especially if they are getting other figures of that scale for the holidays. Sure while younger bigger doesn't matter, but when they hit that 6-10 mark, kids want even scales for playing what they see on tv or creating their own stories.

Both have decent resale values, but ML is nigh impossible to ever find the variant you want for a decent price. Like Blue Flame ghost rider that never even hit my area.