I have no personal experience with Hi-Beams. Lo-Riders were my first DR string and I fell in love with them and haven't used another roundwound string since I found them. However, from what I've heard, Lo-Riders have a push in the low-mids, which give them a somewhat deeper sound in the mix than Hi-Beams even though they have similar low end output. I've also heard that Lo-Riders have more "growl" than Hi-Beams, which wouldn't surprise me based on my experience with them.
But, for me, the feel is the key. I initially chose Lo-Riders over Hi-Beams because I heard that they had more tension. I tend to play with a heavy right-hand technique, even when I'm trying to lay back and be smooth. So things get a little sloppy when I play a string with lower tension. The higher tension of the Lo-Riders lets me play the way I want to play. Oh, and the slap tone is AMAZING! Not a Marcus type of slap tone, a little grittier sounding. I can't imagine a better string for finger-style rock. Also, they don't destroy my hands or my frets and they last a really long time. They aren't perfect for everything, I'm currently in search of a smoother-sounding roundwound that has similar tension for a smooth jazz project I'm working on (nickel Lo-Riders will probably be my first experiment), but what they do, they do really well and they are definitely my favorite string overall out of anything I've played.
I would imagine that the Hi-Beams and Lo-Riders aren't worlds apart; after all, they are both stainless-steel roundwounds within a single brand name. But, both sets have their share of devoted users, so obviously there are differences. There are a lot of threads that compare the two if you search for them. I can't say that they'll work for you, but they are very nice and you may find that, while its a different flavor from Hi-Beams, there are some instances where the Lo-Riders have a better feel or sound.