I entered Munich 10 figuring it to be lighter without knowing what it is.
I'm also unsure of what the default scale for IBU's is.
Is the gravity different for the different Munichs?
All I know off hand is what my software tells me

In Brewtarget, I've got Munich Malt, Munich Malt 10L, and Munich Malt 20L. Here's what each says:
Munich Malt: 9.0 SRM, 80% yield
Munich Malt 10L: 10 SRM, 77% yield
Munich Malt 20L: 20 SRM, 75% yield
Based on that, it does look as though you'll get a little bit less of a gravity contribution as the color gets darker.
Switching from Tinseth to Rager for the IBU approximation actually doesn't change much. I go from 19.8 to 19.2 respectively on the 5.5 gallon batch.
My results are usually close and sometimes spot on. But with improper mash temps in the past I cannot say that it wasn't me.
I noticed Brewtoad gave closer numbers when they first took over Hopville, which is what I used prior. I entered what I had used and noticed our numbers nearly matched.
I've been a bit unhappy with Brewtoad for other reasons, but have kept using them as I'm familiar with it.
I liked Hopville, too, although I didn't use it much before I just downloaded Brewtarget. I keep telling myself one day I'll get Beersmith like everyone else, but I've always been a fan of open source software and Brewtarget just seems to do everything I need so switching hasn't been a priority.