I am looking into some clothing for my SB

Even though I have the measurements Im a little worried I will get the wrong size.
The website I am buying from the size medium and large are not far off each other, do you think I should go for the larger size?
I think clothes are better if they are a little big then too small? because at least then they can be taken in, if they are too small they are pretty useless dontcha think?
I was just wondering if you think I should go for the bigger size just in case? I dont want to dissapoint our buddy.