R18S vs R19S vs R13M

[skybotch]

I realize that the R19S is da bomb in light air but how would an R18S +6 compare to an R19S +8? (on a 160). I assume the R18 could go into a higher wind range but would give up a bit in the light stuff.

I also would like to know how it (R18S +6) would compare to my older R13 M +8. Would their benefits Thickness/Softness offset each other and overlap too much?

Any help would be appreciated.