campy harder to shift then shimano?

[wyver]

the reason I am asking is the fellow who built my bike (a bike messenger) put on a shimano 800 rd over a campy because it took less effort to shift (using sacks ergo shifters)
the cluster is campy but has shimano spacers. but I wanted to go up to bigger sprocket 28t verses the 23 on there now. the shimano 600 rd has a bent arm that was bent back but I would like to replace it. I have a campy chorus rd handy.
so when I get the new cluster I want to know if I should leave it campy and use the campy rd or get another shimano and use the spacers from the old cluster.

[wyver]

even though they are pretty much campy in design? go figure.
I don't mind using shimano now that I know. I just have to make sure to replace the spacers on the cogset.
now I want to get a 27 or 28t cogset. what decent shimano RD should I get? I have a 600 right now bit it is a bit bent so it could use a replacement.

[imtodzzz]

Correct me if I'm wrong, but I believe you can use Shimano shift cables with a Campy system (Shimano cables slightly thinner?) and not vice-versa?!?