Ms word or pages 09

I've always used word2003 to write in ( mainly because it's in my opinion very good in correcting spelling and grammar and my english is not always that good ) I never had a mac and so never used it's word processor , now I do might buy one , but how good is pages 09 compared to ms word ?

Yes,i know that there's a mac version of word , but I assumed that it's almost the same as the windows version .possitive differences in the mac version then ?