Spoiler for those too lazy/busy to scroll: Having played with Lash King for two months, Lash Expander Frame Plus remains my favourite.
Lash King packaging
Tube next to Lash Expander Frame Plus (loathe the cheap-looking new colour-scheme)
Lash King has a traditional bristle brush head, bigger than LEFP's double sided plastic comb. And many more fibres. SO.MANY.Fibres.
For reference: LEFP (wand brushed through upper lashes once)
Lash King: wand brushed through upper lashes once
The most obvious difference is that Lash King gives more volume than LEFP.
Both mascaras are equally: waterproof/smudgeproof, lengthening, capable of holding a curl for days, difficult to remove (requiring Heroine Make Mascara Remover before cleansing oil).
But unforgivably, Lash King's drier formula combined with its, uh, exuberance of fibres means that I experience flaking throughout the day, ending up with a speckled semi-circle of soot under my eyes, which is indelible as only Japanese mascaras can be...
Aside from the flaking issue, Lash King looks best when applied in one clean coat, as above, but I for one am incapable of ever calling it a day after one swipe of mascara (and risk leaving a fraction of inner and outer lashes nude?!), and this formula starts clumping lashes together right from the second pass. Here's a more realistic application with actual eyeshadow on (Suqqu Koju quad, Nars Gaiety under brow), having brushed the wand through about three times:
I ordered Lash King from ct_taiwan for around £12; it's now also stocked at adambeauty, ichibankao and the usual suspects.