holding half press headstand position is for some reason much easier than holding L sit, curious as to the reason why

While working on preparatory elements from H1 I experimented with pressing into a headstand, apparently I can do both straddle press and pike press but what surprised me is that I can raise my legs to 90 degress in a headstand and hold them there with only a moderate degree of effort whereas holding L sit for the same amount of time requires much more effort. so I wonder if L sit is a more disadvantaged position than a headstand where you hold your legs parallel to the floor, I mean looking at the two positions you would think that they would require a similar degree of exertion from your core musculature, they work I suppose the exact opposite muscle groups in your core ( one posterior chain and the other anterior)  . But from a biomechanical perspective I suppose both of them should take a similar degree of effort since on the face of it those positions are very similar.  Of course it would be more interesting to compare L sit to half press handstand but unfortunately I can't lower my legs to 90 degrees in a hanstand yet, but I suppose it's because my shoulders aren't strong enough yet. 

Any thoughts?

Butts are very large compared to hip flexors

Edit: USUALLY...

Jason Dupree said:

Butts are very large compared to hip flexors

Edit: USUALLY...

thought as much, but makes me wonder what's the biological purpose of it, you'd think that hip flexion is as important as hip extension.

If your butt and hamstrings are tight, the L-headstand doesn't really need any strength to hold the position other than just general tightness.  Gravity is actually helping here and giving a nice stretch.  For the L-sit, your hip flexors have to overcome all this tightness as well as fight gravity.

Now try this experiment:  Lay on your stomach and try to lift your legs a couple inches off the ground.  Then roll over and lift your legs a couple inches off the ground.  It's the same muscles as in your L example, but at the other end of their range of motion.  Now it's hip flexors restricting the movement and your glutes aren't a problem.