Roller bits & Myler v. Sprenger

[sfward]

Ok 2 questions really for all you bit experts! Firstly, would a bit with a roller be a good solution for a horse that can get a bit 'dead' and heavy in the mouth? Seems to me the extra movement and play might encourage them to come a bit lighter and off the hand as they'd be playing with the roller rather than fixing on the rein?

Secondly, what do people prefer out of the Sprenger WH Ultra:

Or the Myler Comfort snaffle with copper roller:

Shop4bits only seem to stock the myler with full cheeks, don't know if it's available in loose ring?

Or are there any other roller bits that might be good?

thanks!