I chose my RB67 primarily for how modular it is, but equally for the excellent quality, durability and reliability it offers. I love the interchangeable and rotational aspect of the Mamiya RB67 film magazines - i can carry one magazine loaded with color film and another with b&w and be ready for about anything i'm going to photograph. That Mamiya Sekor lenses are superb was my 1st criteria, but the overall photographic experience the RB67 offers combined with the other "boxes" it checks made it a "no-brainer" medium-format camera choice for me.
I've not tried any slide film (yet), but your (OP) results look very good. It's hard to tell from just seeing the images on a computer monitor, but they certainly look good enough for 16x20 print size without too much loss.
For me, the additional hassles of sheet film and large-format system requirements simply weren't enough to overtake the benefits of the larger negative real estate.