Having seen all three, I can say that the Strike Witches prelude has a superior score, and is better in that it has propeller and machine gun sound effects, but is otherwise inferior to Sky Girls in nearly all other aspects. However, the comparison is somewhat academic because Sentou Yousei Shoujo Tasukete! Mave-chan owns them both.
The Sky Girls unit patch is pretty cool. I think I even like it better than the Mithril unit patch from the Full Metal Panic! series.
I'm disappointed that the Sky Girls TV OP and ED aren't better, although I do admit that the OP sequence featuring Ichijo leaping into her seat is a thing of beauty.
Is it too late to talk about Sky Girls? I enjoy the Sky Girls OAV and want to like the Sky Girls television series on principle, but to tell you the truth, it's sort of dull. As I've lamented before, J.C. Staff's weak point seems to be its unremarkable fight scenes. That's the kind of shortcoming that can really drag down a concept like Sky Girls.
For better or for worse, J.C. Staff also takes the high road as far as fan service is concerned. On its face, Sky Girls appears to be an excuse to parade teenage girls vacuum-sealed into skin-tight outfits every week. While it is true that these Sky Girls pilots wear flight suits offering little to the imagination, they also modestly cover themselves up with double-breasted overcoats most of the time unless they're actually piloting. In fact, they wear overcoats even when the episodes take place in tropical locations. So while there is some fan service in Sky Girls, there's not nearly as much as one might imagine. In fact, the most daring samples appear during the show's OP: (1) Eika shoots a smoldering glare over her shoulder. Ooh la la. (2) Eika takes a running leap into her seat—A.K.A. Ass Shot of the Year 2007 (unofficially).
Instead of being a boobs and butts extravaganza or a post-apocalyptic distopia with savage mecha fights, Sky Girls devotes itself to character-driven stories. Those aspects aren't bad, but probably aren't the reasons why most viewers watched Sky Girls TV in the first place. Those with prurient interests will find the series quite tame, and those looking for full-on mecha battles will find the show dull. Viewers curious about how an eclectic cast of pilots interact will enjoy the series more.
This is a nice group of characters. All the girls are charismatic. Ayako Kawasumi plays Otoha with the chipper feistiness she's so good at. I'm a sucker for the ol' Yui Horie sweetness; there plenty of that, too, with her Nanae. Eika is the best girl, easily, mostly for glaring all the time. The male characters are mostly dullards, but Otoha's grandfather kind of looks like Neko-sensei from Princess Tutu. It frightens me a little.
Sky Girls TV is mostly harmless. It takes no risks and offers little to offend or titillate. The series plays it safe, so viewers are treated to a show that's neither especially good nor especially bad. Perhaps its reception would have been better had Sky Girls been a Gonzo travesty or a controversial, avant garde Gainax vehicle. Really, J.C. Staff should have approached Sky Girls the way it did with Oku-sama wa Mahou Shoujo and The Melody of Oblivion. Or would that have been too dirty? Barring a second season of Sky Girls TV, the world will never know.