Even a Holga can beat your Nikon? I find that surprising. By reputation their optics are poor but perhaps I've heard wrong. The price seems to be right. Which Holga do you have?
The bare bones plastic lens 120N.
It doesn't happen all the time but the center of the Holga's view is quite sharp.
Caveat, I'm not an F-64 type guy the soft edges and built in vignetting don't bother me a bit.
This effect can make for less work at the enlarger in many shots.
This camera makes snaps look really cool.
but I've never, ever worked with larger negatives so I may not know what I'm missing.
It's not just the negative, composing is such a pleasure on an RB's ground glass.
Thus I want to try 120 but I don't want to invest a lot because I don't want something that is an order of magnitude harder.
If there is no rush, MF isn't really that hard, by this I mean only that it takes some practice and planning and certain subjects may be tougher.
At a drag race, a 35mm camera with a motor drive is a great choice.
Doing a portrait of a willing subject in the pits or a landscape shot tough changes the equation, 10 shots of a single subject is about right. With 35mm I find it tough to fill a roll with a single subject, that means I waste some film or have film "stuck in the camera" waiting for another subject.
The other thing to keep in mind along this line is that because of the differences in the look, the constraints, and the logistics of MF; you will think differently when you use it.
What I'm saying is that once you get a feel for an RB or a Holga you will find you reach for them for the personality they bring to certain shooting situations.