As it happens ...
... I started using Rio when I started fly fishing almost nine years ago and that is the only brand I use.
Personally, I think the Selective Trout II is an excellent fly line for general use in Idaho and Montana, and for me, I think it would work well in other parts of the West.
There are several things that have happened that bear on the situation you are describing, at least as it relates to Rio.
First, because of the growth of Spey and the addition of Simon Gawesworth to the Rio staff, some of Simon's ideas about Spey lines have crossed over into designing conventional fly lines. Or so it has seemed to me as I watched it happen over the past five or six years. That is just my impression, and maybe Rio would have something markedly different to say in that regard.
Second, when Sage decided to do the bass rod thing, their sibling Rio wanted to compete in that specialty, also.
Third, the growth of interest in fly angling for carp had a similar effect, adding new designs to Rio's line. I can tell you that one of my friends down in Idaho Falls helps coordinate the annual carp weekend down there and one of our mutual friends is the General Manager of Rio in Idaho Falls ( at least as of a couple years ago ). It's not hard for me to imagine Kinley talking to John about what he would like to see in a line designed for carp angling.
I think Scott's recommendation above is excellent advice - the part about bringing the question to the BB. Of course, I would have recommended the Selective Trout II or LT lines, so there you have it.
John
P.S. And then if you want to get into price point ( read Mainstream ) or rod action ( read Grande ) .....
The fish are always right.