About matching Oz's performance, is not an excuse. Watch "From Puppet's to Pixels" and listen to the audio commentary of Episode II and Rob Coleman specifically states that after talking with Oz, the animators came to the realization that they technically could go beyond what Oz did, performance wise, but that would be a mistake. He wouldn't be Yoda. They purposely tried to match every move, every nuance that Oz did with that puppet, while "loosening" him up just a tad around the lips.

ILM and Weta both had difficult tasks because those two character had to intergrate with the live actors they came into contact with. Look at every scene with the two characters, they're always with a live actor for the most part.

I just personally feel that ILM did it better than Weta mainly because of lighting. As good as they are, Weta can't light for shit. Just look at the Rings Trilogy and Kong. They get it half right and half wrong all the time. With ILM, they tend to get it right 85% of the time.