1-1/2" Vs. 2" foam?

Are there any advantages to using 2" foam over 1-1/2"? I know when building a teardrop, every inch counts. I'm thinking I can gain an extra inch in the inside width of my teardrop by using 1-1/2" foam instead of 2". I do not plan on using plywood as a support. Since I am in the planning stages at this point I thought I would ask the question to the more experienced foam builders.
Thanks,
Dave
Thanks,
Dave