The Radas made for 4x5 backs were simply packed out in the base, for Plaubel in the main since it was their company. The Rada is the least good of the roll designs (ignore Rollex completely).
Main considerations are going to be how it fits with your glass back, what kind of winder, and price. You have to be certain that the registration of the glass surface and film plane is perfect. Compare using your original 4x5 glass with using an adaptor and a separate, smaller glass frame for your format.
Knob wind is nice and simple, but if it's a fat one it may be awkward against the edge of your frame. A single lever stroke would be quicker to use. OTOH, the Linhof I have has a good film counter so I'm not going to complain about awkward in this case. The better-made ones tend to be on the heavy side.
Shen-hao made a lovely slide combo with a 6x9 glass and a 6x9 film holder, but it's really an extra wooden back to carry. I think several companies made these in metal for their rail cams.
I also bought it with colour in mind but in fact I still haven't used my Linhof 6x9 since I picked it up last year at Photographica at the end of the day for £25. List price was £45 but the seller was clearly feeling tired and couldn't resist any further.