I have a 2.8F with prism, a Pentax 67, and a Bronica ETRS with prism.
I don't find the Rollei with the prism difficult to use at all, and I've been using it this way for the better part of a year. Yes, it's a little awkward to hold, but you get used it it. Or at least, I did. I've used it for portraits (the prism is indispensable for that) and for street photography.
The Pentax 67 is definitely handhold-able, but heavier and larger. I love that camera. Handles exactly like a large 35mm SLR.
Of the three, I find the Bronica the most awkward to hold while using it with the prism (without a grip).
Not sure if this helps...