区别就是两者都是单词perfect的派生词，具体的不同如下

perfectness为形容词的派生词，中文意思是. 完美，分毫不差精通

So eat what you want， don't go the wrong way to pursue perfectness.

perfection为动词的派生词，中文意思是. 完美完善完美的人（或物）The novel achieves a perfection of form that is quite new.