Straddle casts are easier, there's more room for incorrect technique as well (though not much). Some gymnasts may be able to straight body cast to a handstand, but they arch their backs terribly and that results in more deductions. If good form and a hollow body are possible, then by all means go for it.
In JO straddle and straight body casts are worth the same thing. In elite they are not, straight body casts are worth more.
Piked glide swings require more abdominal and hip strength, but are better for gymnasts with hip problems.
Personally, when I do kip casts my first glide is usually a straddle to generate more speed, but after my first handstand or skill I do all piked glides.
We worked both types of casts at my gym (unless you're weak and old like me, I only did straddle) and the coaches didn't care about our glides as long as we had straight legs, pointed toes, and didn't kick the mats if a coach was spotting.
What is more desirable? It depends on coach personal preference. If at all possible coaches usually strive for straight body casts because they show more strength and less likely that legs will bend and toes will flex.