他们的区别是：
used to 是
情态动词，一般后跟动词原形：used to do 表过去常常做某事。
be used to（do） 是use的
被动语态结构，表某物被用来做某事。
use to 通常出现在be no use to sb，对某人来说是无用的。be of use to sb对某人来说是有用的，有帮助的，在这里作名词。
例句辨析：
Use to
1、This medicine is of no use to me.
此药对我无用。
2、I'm sorry, I've been no use to you.
对不起，我一点儿忙也没帮上。
3、It's no use to say anything. I'll sue you.
说什么都没用了。我会控告你。
used to
1、I feel more compassion and less anger than I used to.
我觉得自己比过去多了些同情，少了些怒气。
2、A kid I used to be friends with turned against me after being told that I'd be eninsulting him.
曾和我很要好的一个小孩听人说我一直在辱骂他以后就和我翻脸了。
3、The machines start to wear down, they don't make as many nuts and bolts as theyused to.
机器开始出现磨损，螺母和螺钉的产量不如从前了。