I don’t think either version was ‘better’ per se, except maybe in the sense of being better suited for the specific task being asked of Soundwave at the moment. My preference, however, as in I got a kick out of looking at him and watching what he did would be the variant of Soundwave in Revenge Of The Fallen.
Reasons: DOTM Soundwave looked fine and all as a robot and his car mode was pretty, but there were other robot/car combos that looked equally good to me—he didn’t stand out for me, visually. I also can’t remember him doing anything spectacular enough to stick with me. And the surprise of Soundwave being Carly’s ‘loaner’ car? Didn’t work, or rather wouldn’t have worked, even if I hadn’t known beforehand. Carly’s boss just played it WAY too creepy right from the start…(thank you, Captain Obvious)...
ROTF Soundwave, though…ah, now he was different! Him I remember. And the scene of him first infiltrating that satellite was so creepy and alien and a little disturbing--heck, even some critics who slammed the movie picked up on that visual and praised it. He was also directly responsible for giving me one of my favourite eye-popper scenes—sending Ravage to retrieve the shard—and I’m sure he had something to do with making possible one of my favourite totally inane scenes: Judy Witwicky mistaking Megatron for an obscene phone caller and hanging up on him! (What the--???) That’s enough for me to like ROTF Soundwave better.
Even in the movieverse, Kickback remained unclear on the concept.