1、“确实”比“实在”更书面，正规。using in written english
“实在”一般用于口语中。using in oral english
2、都可以用来肯定，赞同别人说的话。“确实”较为客观，有事实依据的肯定(have impersonal proof)，“实在”更多主观同意，感情比确实更强烈(more subjective)。如：
我的答案确实是对的。My answer is certainly right.
我实在找不到错误。I really can't find the error.
我实在找不到书，你确实放在桌子了？
I really can't find the book,are you sure you put it on the desk?
3、“实在”用来夸诚实，真诚
例：他人很实在 he's a kind person
这家饭店的菜很实在。“实在”表示菜（肉）给的很多，量大。
The dishes in this restaurant are huge ,cheap and delicious.
