I've used both these strings, and like them both for different reasons.
Roto 77s have reasonably high tension, and are bright for a flatwound. They also have a very smooth feel to them, and you might not like this, as your fingers may slip a little on the string as compared with round wounds.
I have a set of these on my Filakovsky Jazz bass right now which has Sadowsky pups and the VTC circuit.
This bass is my Motown Machine.
I've also used the DR Lo Riders on my Stingray 4, and loved them.
They're a bit stiffer than most round wounds, but I liked the feel.
Once you've had them on your bass for a few days, you'll realize how predictably they respond between a light touch or digging in.
If you're asking for an opinion on which set to buy, I'd recommend the Lo Riders as a starting point.
I think you'll be happier with them than with the Roto 77s.
Also, if your bass is a 5 string, I would recommend getting a tapered B string for whichever set you get.
I once had a set of Lo Riders on my Ibanez BTB1205E, and the B string, which wasn't tapered sat up much too high on the saddle, and was lower in volume than the other strings.
Good Luck.
Mike
