I'm also a UC fan but I don't think all the designs in Seed are doo doo. I think the first five Gundams were interesting (I am especially fond of the Blitz) as was the Freedom (in design, not it its "OMG!! ITS A GUNDUM!!" skills) and a majority of the bad guys designs.
Destiny is more of a crappy suit fest and I think that has to do with the fact that Kunio Ookawara was fully in charge of designs (though I know it's not his fault since Bandai is in charge). The first suits we were introduced to were garbage with the exception of the Gaia. After that it wasn't until the Windham showed up that I actually went "that looks pretty ok" again.
The Destiny Gundam was Ok, I just thought it could use a new paint job. Infinite Justice was awesome and I hate pink and thought the original Justice looked like utter crap. Akatsuki, well I can't figure out if I like Akatsuki cuz it looks cool or because its a rip off of Hyaku Shiki which is my favorite non Gundam Feddie MS.
The grunt ZAFT suits in Destiny suck and I still don't know why Bandai allowed the designs to take a step backwards compared to the first show. In my opinion:
GINN >> Z.A.K.U.
GuAIZ >> GuAIZ R
CGUE >> G.O.U.F. Ignited etc.
The only bastardized design I liked was the D.O.M. and I can't even figure out why to be honest. I hope Ookawara cried when he mangled the Zaku and Gouf or he designed them badly on purpose because Bandai was being ridiculous in tossing them into the CE.
Junichi Akutsu, the guys at Bee-Craft and anyone else involved in Astray should be primary designers, then at least if the show ends up being crap, we can ignore it and build kits of great Mobile Suits. Hell the Astray series is practically the only saving grace of the Seed world. Good story, characters AND designs. No wonder Bandai didn't animate it