Which size to get?

I'm 510 180 with a chest size 42. sleeve and waist size matches meduim but chest size is in between meduim and large. Which size should i go for large or medium?

Update.
I ended up going with Large. It was a little loose and the arms a little long. The hood was bothersome too. I can see this working if I wanted to work a lot of layers underneath but I just wasn't feeling it.

So I ordered a Medium. Its a much better fit. I can still layer a little underneath but I don't plan on doing a midlayer underneath just a good base layer. This after all will be my baselayer for my shell on cold boarding days :) The only thing I don't like as much is the length was better on the large.

Thanks for the answers' guys I just wanted to update this so everyone else could benefit if possible.
As Dave mentioned below your millage may vary depending on your use for this jacket.

Tech Specs:

Material:

Luminara nylon, Polartec Power Stretch with HardFace Technology (88% polyester, 12% spandex), DWR coating 

Insulation:

Coreloft (60g) 

Fabric Waterproof Rating:

water-resistant 

Hood:

yes, fixed 

Fit:

trim 

Length:

hip 

Pockets:

(external) 2 front hand, (internal) 1 zippered 

Weight:

13 oz 

Recommended Use:

layering, cold weather exploration 

Manufacturer Warranty:

lifetime