Replying to Sessions Pants Sizing

I have a question about Sessions pants.  I'm about to order the "chemical pant" in heathered hershey color.   Anyway, I was just wondering how the sizes of sessions are and how the XL and L differ.  I was going to go with a large, but if igured i should go XL just in case. 
I'm 5'8" and 150.  Currently i'm using XL HH embargo pants, which are pretty parachutie near my waist, but are fine lower down. 
Basically i just want to know if XL will make a bigger difference other than making the waist huge.  because i don't really want a huge waist anymore.

ha, okay, thanks.