The bio-fin XTs (and other splits) will frog kick, as you've noticed. As you've also noticed, their frog kick can't hold a candle to the frog kick Jets put out.
I think that most of the people who say "my splits can frog kick just fine!" have never directly compared the two, or have technique that is so poor they truly can't tell the difference.
As long as you use the small flutter kick from the knee, in decent conditions and with a wetsuit, splits will smoke a pair of Jets. It can be frustrating to keep up with someone in splits during a long surface swim. All this with lower gas consumption and less knee strain, too.
But, add in a drysuit and doubles, and situation changes. Or, try putting a Jets-wearer and a split-wearer on a muddy bottom, with both doing frog kicks, and the Jets will cream the splits, all else being equal. They may both do a proper frog kick, but only one will do well... and the difference will be very obvious, side by side.
And that's no even getting into helicopter turns, backwards, etc.
Splits have their strengths. They have their weaknesses, too. You have to decide which is more important for you, given the kind of diving you do.