区别是：old man统指上了年纪的人，older man指年龄相比而言年龄较大者，例如：
1、An older man came out with a little dog on a lead.一个年纪较大的男子牵着一条小狗走了出来。
2、The older man asked in his oily voice what he could do for them today.年长的那个男人声音谄媚地询问今天能为他们做些什么。
3、She's having a relationship with an older man.她跟一个比她大的人有染。
